Parasubiculum


Ionic conductances that generate membrane potential oscillations in neurons of layer II of the parasubiculum were investigated using whole-cell current clamp recordings in horizontal slices from the rat brain. Intrinsic membrane potential oscillations in neurons of layer II of the parasubiculum are therefore likely driven by an interaction between an inward persistent Na(+) current and time-dependent deactivation of Ih. These voltage-dependent conductances provide a mechanism for the generation of membrane potential oscillations that can help support rhythmic network activity within the parasubiculum during theta-related behaviors..  

Four cats then received electrolytic lesions restricted to the posterior parahippocampal region (experimental group) including mainly parahippocampal cortex, parasubiculum and presubiculum.  

Prominent Wfs1 expression was seen in the hippocampal CA1 region, parasubiculum, superficial part of the second and third layers of the prefrontal cortex and proisocortical areas, hypothalamic magnocellular neurosecretory system, and central auditory pathway.  

In postnatal brain, expression was prominent in the cortex, subiculum, parasubiculum, granule neurons of the dentate gyrus, and some brainstem nuclei.  

The parahippocampal region in the rodent brain includes the perirhinal, postrhinal, and entorhinal cortices, the presubiculum, and the parasubiculum.  

Projections from the remaining cingulate areas preferentially target the postrhinal and medial entorhinal cortices as well as the presubiculum and parasubiculum.  

We recorded neurons in the MEC, parasubiculum, and CA1 and head direction cells of the anterior thalamus as the rat's internal direction sense was pitted against a salient visual landmark by slowly rotating the rat in a covered bucket while counter-rotating the visual cue.  

First, the results confirm and extend known intrahippocampal formation inputs to dentate gyrus, subiculum, presubiculum, parasubiculum, and entorhinal area, which are arranged generally along the formation's transverse axis and dominated by the subicular projection-by far the densest established by field CA1 anywhere in the brain.  

There were also very substantial projections to the entorhinal cortex, presubiculum, and parasubiculum of the hippocampal formation, as well as to areas TH and TF of the parahippocampal cortex.  

The parasubiculum is a major component of the hippocampal formation that receives inputs from the CA1 region, anterior thalamus, and medial septum and that projects primarily to layer II of the entorhinal cortex. The present study was aimed at determining if theta is also generated locally within the parasubiculum versus volume conducted from adjacent structures. In urethan-anesthetized rats, the phase-reversal of theta activity between superficial and deep layers of the parasubiculum was demonstrated using differential recordings from movable bipolar electrodes that eliminate the influence of volume-conducted activity. These results indicate that theta field activity is generated locally within the parasubiculum and that intrinsic membrane potential oscillations, synchronized by local inhibitory inputs, may contribute to the generation of this activity..  

Alterations in superficial layer circuitry were suggested by showing that presubiculum, parasubiculum and deep MEC stimulation evoked 100-300 Hz field potential transients and prolonged EPSPs (superimposed on IPSPs) in superficial MEC which were partially blocked by APV (in contrast to control) and fully blocked by CNQX.  

Specifically, RE projects strongly to the medial frontal polar, anterior piriform, medial and ventral orbital, anterior cingulate, prelimbic, infralimbic, insular, perirhinal, and entorhinal cortices as well as to CA1, dorsal and ventral subiculum, and parasubiculum of the hippocampus.  

The first major wave of apoptotic neurodegeneration occurred at 8 h postimpact in the retrosplenial cortex and pre- and parasubiculum.  

The term "hippocampal formation" is defined as the complex of six structures: gyrus dentatus, hippocampus proprius, subiculum proprium, presubiculum, parasubiculum and area entorhinalis In this work we attempt to present a brief review of knowledge about the hippocampus from the point of view of history, anatomical nomenclature, comparative anatomy and functions (Tab.  

The medial subdivision is located at the border of the parasubiculum and is characterized by a narrow cortex, wide layer II, and densely packed cells in layer V.  

To investigate the role of the entorhinal cortex in memory at a molecular level, we developed transgenic mice in which transgene expression was inducible and limited to the superficial layers of the medial entorhinal cortex, pre- and parasubiculum.  

This includes an apparent increase in the density of projection to areas that normally receive CA3 outflow such as CA1 and subiculum as well as novel projections beyond the confines of the hippocampus to the pre and parasubiculum and medial and lateral entorhinal cortex.  

The presubiculum, but not parasubiculum, was strongly reactive for glycogen phosphorylase.  

the subiculum, presubiculum, parasubiculum and entorhinal area, and the adjoining neocortical perirhinal and retrosplenial cortices of the New Zealand white rabbit.  

The projections from the perirhinal cortex, entorhinal cortex, parasubiculum, and presubiculum to the thalamus were examined using both anterograde and retrograde tracers. These relatively light projections, which arose from all areas of the entorhinal cortex, from the presubiculum, parasubiculum, and area 35 of the perirhinal cortex, terminated mainly in the anterior ventral nucleus. In contrast, the projections to the lateral dorsal nucleus from the entorhinal cortex, presubiculum and parasubiculum were denser than those to the anterior thalamic nuclei.  

Quantitative image analysis showed that approximately half of Kv4.2-positive puncta were closely apposed to glutamic acid decarboxylase-positive boutons in the parasubiculum and dentate gyrus.  

One hundred days of self-administration also induced a higher density of NET binding within the A1 cell group; however, in addition, the effects extended to the nucleus prepositus, as well as forebrain regions such as hypothalamic nuclei, basolateral amygdala, parasubiculum, and entorhinal cortex.  

The question of primary concern in the present research was whether the group of anatomically related structures (hippocampus, subiculum, presubiculum/parasubiculum, entorhinal cortex, perirhinal/postrhinal cortex) are involved in mediating a similar memory process or whether the individual structures are differentially involved in memory processes and/or in handling various types of information. The structures were found to differ functionally, with the hippocampus and the presubiculum/parasubiculum being especially involved in processing spatial information, and the perirhinal/postrhinal cortex having a specific role in remembering information over a brief time period (working memory).  

Decreased PV immunoreactivity was observed within 1 day after SE in the hilus, pre- and parasubiculum, and in the entorhinal cortex layers II and V/VI.  

Calretinin-containing neurons in the hippocampal formation, including the subiculum, presubiculum, parasubiculum, and entorhinal cortex, were visualized with immunocytochemistry. In the parasubiculum, a few immunoreactive bipolar and multipolar cells could be observed in the superficial and deep pyramidal cell layers.  

2) The proximodistal axis of the presubiculum corresponded to the axis from the MEA/LEA boundary to the MEA/parasubiculum boundary that was virtually perpendicular to the MEA/LEA boundary, where the proximal portion of the presubiculum (close to the subiculum) projected to the region near the MEA/LEA boundary..  

To determine what influence the pre- and parasubiculum regions of the hippocampal formation have on neural representations within the dorsal hippocampus, single-unit recordings were made as rats with bilateral ibotenic acid lesions centered on the former regions (n = 4) or control surgeries (n = 3) foraged freely. These findings indicate that the pre- and parasubiculum regions have a major role in maintaining the specificity of the place field firing of hippocampal pyramidal cells.  

Although a major output of the hippocampal formation is from the subiculum to the deep layers of the entorhinal cortex, the parasubiculum projects to the superficial layers of the entorhinal cortex and may therefore modulate how the entorhinal cortex responds to sensory inputs from other cortical regions. Recordings at multiple depths in the entorhinal cortex were first used to characterize field potentials evoked by stimulation of the parasubiculum in urethan-anesthetized rats. Responses of the entorhinal cortex to piriform cortex inputs were inhibited when the parasubiculum was stimulated 5 ms earlier and were enhanced when the parasubiculum was stimulated 20-150 ms earlier. These results indicate that excitatory inputs to the entorhinal cortex from the parasubiculum may enhance the propagation of neuronal activation patterns into the hippocampal circuit by increasing the responsiveness of the entorhinal cortex to appropriately timed inputs..  

After kainate was injected (i.p.), PAI-2 mRNA was substantially and rapidly (within 2 h) induced in neuron-like cells primarily in layers II-III of the neocortex; the cingulate, piriform, entorhinal and perirhinal cortices; the olfactory bulb, nucleus and tubercle; in the accumbens nucleus, shell and core; throughout the caudate putamen and the amygdaloid complex; in the CA1 and CA3 areas of the hippocampus, and in the parasubiculum.  

Thereafter, we focused on projections to the hippocampal formation (dentate gyrus, hippocampus proper, subiculum) and to the parahippocampal region (presubiculum, parasubiculum, entorhinal, and perirhinal and postrhinal cortices).  

In the remainder of the cortex, the heaviest projections originated in the hippocampal formation, including the entorhinal cortex, subiculum, presubiculum, and parasubiculum.  

Six of the monkeys then received ibotenic acid lesions restricted to the hippocampal formation (group H), and the four others received selective ablations of the posterior parahippocampal region (group P), comprising mainly parahippocampal cortex, parasubiculum, and presubiculum.  

Layers I and II of the parasubiculum received a light projection.  

These include the presubiculum of the isthmus (PrSi), parasubiculum of the isthmus (PaSi), area 29 of the isthmus (area 29i) and area prostriata (Pro), which has anterior (Pro-a) and posterior (Pro-p) divisions.  

In older mutant mice (16-18 months old), there was also gliosis most marked in the presubiculum and parasubiculum of the hippocampal formation, as well as the entorhinal cortex, neocortex, and striatum.  

The subiculum was the major source of hippocampal projections to the nucleus accumbens, but some hippocampal efferents also originated in the parasubiculum, the prosubiculum, the adjacent portion of CA1, and the uncal portion of CA3.  

Within the subicular complex, a more intense GABA(B)R1a-b immunostaining was found in the subiculum than in the presubiculum or parasubiculum, especially in the pyramidal and polymorphic cell layers.  

Excitatory inputs to layer V neurons of the parasubiculum and medial entorhinal cortex were examined in rat brain slices with intracellular and field potential recordings.  

The perisubicular region, located medially adjacent to the dorsal subiculum may be equivalent to the rat's presubiculum; evidence for the presence of a parasubiculum was rather weak..  

Retrograde neuronal labelling was observed in CA1, subiculum, presubiculum and parasubiculum; it was absent in the dentate gyrus, CA3 and CA2. Our results indicate that CA1, subiculum, presubiculum and parasubiculum send direct output to cortical areas.  

Although posterior area 27 and the parasubiculum are similar to rostral levels, posterior area 36' differs from rostral area 36.  

The entorhinal cortex is medially bordered by the parasubiculum, and laterally by the perirhinal cortex; rostrally and medially it is bordered by the piriform cortex, whereas caudally and dorsally it is bordered by the postrhinal cortex. Further, both the border with the perirhinal cortex and the border with the parasubiculum are characterized by dark-stained bands of AChE. In contrast, in sections stained for calretinin, the entorhinal cortex is more lightly stained than the parasubiculum, which has a darkly stained superficial layer, and a densely stained group of neurons in layer III..  

Serial reconstruction of the ibotenate-induced primary lesion revealed that entorhinal neurons were protected only in animals that had lesions in the pre- and parasubiculum, especially in the deep layers (IV-VI). CONCLUSIONS: The deep layers of the pre- and parasubiculum appear to control the seizure-induced damage of EC layer III.  

FB134 showed a nervous tissue specific expression pattern and an exclusively prominent expression in the developing presubiculum and parasubiculum.  

Rats with bilateral ibotenic acid lesions centered on the pre- and parasubiculum and control rats were tested in a series of spatial memory and object recognition memory tasks. These findings indicate that the pre- and parasubiculum plays an important role in the processing of both object recognition and spatial memory..  

Intracerebral infusions of Na2SeO3 in the lateral dorsal nucleus resulted in retrogradely labeled neurons that were located in the postsubiculum, and also in the pre- and parasubiculum.  

The parasubiculum sent fibers mainly to the medial EC; most densely to layer II.  

The more spatially demanding task in each experiment also resulted in increased Fos expression in the subicular complex (postsubiculum, presubiculum and parasubiculum), as well as in the prelimbic cortex.  

The subdivisions examined included CA4, CA3, CA2, CA1 (CA: cornu ammonis), prosubiculum (PRO), subiculum and presubiculum (PRE), parasubiculum (PARA) and the entorhinal cortex (ENT).  

These pathways terminate in the rostral half of the entorhinal cortex, the temporal end of the CA3 and CA1 subfields or the subiculum, the parasubiculum, areas 35 and 36 of the perirhinal cortex, and the postrhinal cortex.  

In the striatum, hippocampal formation, presubiculum and parasubiculum, amygdaloid nuclei, thalamic nuclei, locus coeruleus, and nucleus ambiguous MOR-1-LI predominated, whereas MOR-1C-LI was absent or sparse.  

Cytoarchitectural analysis confirmed the identity of area prostriata and further clarified its extent and borders with the parasubiculum of the hippocampal formation rostrally, and V1 of the visual cortex caudally.  

For example, in adult NT-3(lacZneo)/+ mice, beta-galactosidase is expressed in high amounts in limbic areas of the cortex (cingulate, retrosplenial, piriform, and entorhinal), in the visual cortex, in the hippocampal formation (dentate granule cells, CA2 cells, fasciola cinereum, induseum griseum, tenia tecta, presubiculum, and parasubiculum), and in the septum (septohippocampal nucleus and lateral dorsal septum).  

Binding in the hippocampal formation was heterogeneously distributed, with dense areas of binding sites seen in the parasubiculum, subiculum, and molecular layer of the dentate gyrus, and the lacunosum-moleculare layer of the CA1/2. These increases ranged from 160% of control in parasubiculum to 290% in the molecular layer of the dentate gyrus.  

The highest densities of labeled cells were observed in the presubiculum, parasubiculum, entorhinal cortex, and subiculum, whereas the CA3 field and the dentate gyrus had the lowest densities of positive neurons.  

Changes in the expression of immediate early gene c-fos by noxious mechanical stimulation to the mandibular incisor pulp of rats were immunohistochemically examined in the hippocampus (Ammon's horn and dentate gyrus) and the retrohippocampus (subiculum, presubiculum, parasubiculum and entorhinal cortex). These decreases reached statistical significance in superficial layer parasubiculum bilaterally (p<0.01), bilateral CA1 and ipsilateral side of superficial layer of medial entorhinal cortex (p<0.05).  

Neuronal loss, astrocytosis, and spongiform change were studied in lesions in the entorhinal cortex, parasubiculum, presubiculum (external and internal principal laminae), subiculum, and prosubiculum, respectively. RESULTS: The results of this study showed that in group I neuronal loss and astrocytosis were more severe in the parasubiculum and the external principal lamina of the presubiculum than in the other regions including the entorhinal cortex, and in group II the lesions in the entorhinal cortex, parasubiculum, and the external principal lamina of the presubiculum were more severe than in the other regions. CONCLUSION: On the contrary, our findings also raise the possibility that the parasubiculum and the external principal lamina of the presubiculum may be the structures most vulnerable to early lesions in the parahippocampal gyrus in CJD.  

The main S100A6-immunoreactive elements were 1) neuronal somata and dendrites in some specific regions of the limbic system (e.g., the basolateral amygdaloid nucleus, ventral tip of the CA1-subicular border region, entorhinal cortex, and parasubiculum), most of which were identified as a subpopulation of pyramidal cells; 2) olfactory receptor cells and olfactory nerve fibers and terminals in the olfactory bulb; 3) some tracts of the hindbrain and spinal cord (e.g., the spinal trigeminal tract, solitary tract, dorsal root fibers, and the tract of Lissauer) and their terminals (e.g., the principal sensory trigeminal nucleus, spinal trigeminal nucleus, nucleus of the solitary tract, marginal zone, substantia gelatinosa, and proper sensory nucleus of the dorsal horn), as well as some sensory neurons of their origins in the dorsal root and trigeminal ganglia; 4) a subpopulation of astrocytes in the white matter (e.g., the corpus callosum, cingulum, external capsule, internal capsule, and fimbria of the hippocampus) and around the ventricles; 5) some ependymal cells, especially around the central canal; and 6) Schwann cells.  

The parasubiculum receives dense projections from the caudal portion of the medial division of the lateral nucleus, the caudomedial parvicellular division of the basal nucleus, and the parvicellular division of the accessory basal nucleus. Our data show that select nuclear divisions of the amygdala project to the entorhinal cortex, hippocampus, subiculum, and parasubiculum in segregated rather than overlapping terminal fields.  

Dendritic elongation of PV-like immunoreactive interneurons and perisomatic distribution of PV-like immunoreactive terminal boutons on their cellular targets were first observed in the subiculum around E127; then from E127 to E142 in CA3/CA2 and layers III-V of the entorhinal cortex and, to a lesser extent in CA1, the dentate hilus and deep granule cell layer; and finally from E156 to postnatal day 12 in the rest of the dentate gyrus, the presubiculum and parasubiculum, and layers III-II-I of the entorhinal cortex.  

Projections from each layer of the entorhinal cortex (EC) of the cat were traced to the dentate gyrus (DG), Ammon's horn (CA), prosubiculum (ProSb), subiculum (Sb), presubiculum (PreSb) and parasubiculum (ParaSb); the anterograde or retrograde labeling method was used after stereotaxic injection of wheat germ agglutinin-horseradish peroxidase, cholera toxin B subunit, or Phaseolus vulgaris leucoagglutinin.  

In the majority of slices from AOAA-treated rats, responses recorded in the superficial layers of the medial entorhinal cortex to white matter, presubiculum, or parasubiculum stimulation were abnormal.  

Mean densities of SPs and NFTs were determined in the hippocampal formation (CA1, subiculum, and parasubiculum) and in six neocortical areas (midfrontal, orbitofrontal, cingulum, fusiform gyrus, superior and inferior parietal cortices).  

After completion of acquisition training (significantly longer latencies for repeated arms in comparison with the first presentation of an arm), rats received lesions of the medial or lateral entorhinal cortex, pre- and parasubiculum, or served as sham-operated controls. Based on continued postsurgery training and additional tests, the results indicated that rats with pre- and parasubiculum or pre- and parasubiculum plus medial entorhinal cortex produced sustained impairment in performing the task. The data suggest that working memory for spatial location information is mediated primarily by the pre- and parasubiculum, but not medial entorhinal and lateral entorhinal cortex..  

gamma-Frequency activity recorded intracellularly from deep layer neurons of entorhinal cortex, presubiculum and parasubiculum consisted of one action potential correlated with each of the three to five gamma cycles recorded with a proximate field potential electrode.  

Inhibitory post-synaptic potentials (IPSPs) were studied in neurons of presubiculum, parasubiculum and medial entorhinal cortex in horizontal slices from rat brains.  

Afferents from cingulate area 25, the retrocalcarine cortex, temporal pole, entorhinal cortex, parasubiculum, and the medial part of area TH target primarily or only area 24c.  

In CJD, pathology was severe in pre-parasubiculum and temporal cortex, and little or absent in CA1-4; PV+ neurons were severely reduced or absent in all cases, whereas Cal+ neurons were largely preserved. In controls, the density of PV+ neurons was highest in pre-parasubiculum and temporal cortex, and lowest in CA1-4.  

Although the retrohippocampal region (presubiculum, parasubiculum, and entorhinal area) is an integral part of the hippocampal circuitry and is affected selectively in a number of disorders, estimates of neuron numbers in the rat retrohippocampal region have yet to be published. A surprising finding was the large numbers of neurons in the pre- and parasubiculum, which indicate an important role of these areas in the control of the entorhino-hippocampal projection.  

The hippocampal subdivisions examined included: CA4, CA3, CA2, CA1, prosubiculum, subiculum and presubiculum (PRE), parasubiculum (PARA) and entorhinal cortex (ENT).  

The pre/parasubiculum contributed with area 29 m to the lateral bank of the calcarine sulcus as far as the most caudal extent of the hippocampal formation.  

The presubiculum and parasubiculum are retrohippocampal structures bordered by the subiculum and medial entorhinal cortex. Extracellular stimulation of the subiculum, deep medial entorhinal cortex or superficial pre- or parasubiculum caused, in deep layer cells only, a short latency burst discharge which could be followed by one or more after-discharges. In intact slices, superficial layer neurons of pre- and parasubiculum could exhibit EPSPs coincident with bursts recorded in the deep layers. However, in isolated subsections of horizontal slices or in 'vertical slices', both of which contained only pre- and/or parasubiculum, evoked or picrotoxin-induced bursts occurred only in deep layer cells. Antidromic population spikes confirmed projections from superficial cell layers of pre- and parasubiculum down to their deep cell layers. We conclude that the deep layer cells of the presubiculum and parasubiculum are richly interconnected with excitatory synapses. The absence of significant ascending input can account for the functional separation of superficial and deep layer neurons of presubiculum and parasubiculum..  

In the presubiculum, retrosplenial area 29e, and parasubiculum, neuropil staining first appeared by P3. This occurred first by P28 in the parasubiculum due to the late maturation of the parasubiculum a. Labeled cells were first seen by P7 in layer III of the presubiculum and by P15 in the retrosplenial area 29e and the parasubiculum.  

Stellate cells were recorded in layers II and V of presubiculum and parasubiculum. Pyramidal cells were recorded in layers III and V of presubiculum and layers II and V of parasubiculum. Both pyramidal and stellate cells in the deep layer of pre/parasubiculum could exhibit population bursting behavior in response to stimulation of subiculum or entorhinal cortex.  

The largest decreases in the densities of positive fibers were observed in the dentate gyrus, CA3 and CA2 fields of the hippocampus, subiculum, parasubiculum, and medial and caudal parts of the entorhinal cortex. The presubiculum demonstrated remarkable sparing that contrasted with the almost complete loss of fibers in the parasubiculum.  

Entorhinal cortex infusion retrogradely labeled neurons within the perirhinal cortex, endopiriform nucleus, piriform cortex, dentate gyrus, presubiculum, parasubiculum, CA1-CA4 fields, amygdaloid nuclei, basal forebrain, thalamus, hypothalamus, periaqueductal gray, raphe nuclei, and locus coeruleus.  

Thus, the highest levels of immunostaining were observed in the islands of Calleja, diagonal band of Broca, magnocellular preoptic nucleus, pre- and parasubiculum, suprachiasmatic nucleus, anterodorsal nucleus of the thalamus, substantia nigra, ventral tegmental area, pontine nuclei and dorsal motor nucleus of the vagus, all of which had previously been documented to contain high densities of neurotensin binding sites.  

Immunohistochemical studies in Zamboni-fixed rat tissue demonstrate immunoreactive perikarya and/or fibers in such regions as the deep layers of the parietal, temporal and occipital cortex, parasubiculum, central and medial amygdala, bed nucleus stria terminalis, nucleus accumbens, olfactory tubercle, endopiriform nucleus, claustrum, hypothalamic nuclei, median eminence, midline thalamic nuclei, zona incerta, central gray, caudal linear and dorsal raphe, substantia nigra, pars reticulata, ventral tegmental area, parabrachial nucleus, spinal trigeminal nucleus, nucleus of the solitary tract, spinal cord and the dorsal root ganglia.  

In the subicular area, there is a lateromedial decreasing gradient in immunostaining intensity, the subiculum being moderately stained and the parasubiculum weakly stained.  

The subdivisions examined included CA1-4, prosubiculum (PRO), subiculum and presubiculum (PRE), parasubiculum (PARA) and the entorhinal cortex (ENT).  

A moderate number of Zif268-immunopositive neurons were located in the parasubiculum and the number of these neurons in the subiculum proper was smallest among the three subicular subdivisions.  

The highest densities of labeled fibers were observed in the uncal portion of the hippocampus, in the parasubiculum, and in the entorhinal cortex; the lowest densities of labeled fibers were observed in CA1 and in midrostrocaudal levels of the dentate gyrus. The density of choline acetyltransferase staining was high in the presubiculum and parasubiculum.  

The immunohistochemical localizations of two specific calcium binding proteins, calbindin D-28K (calbindin) and parvalbumin (PV) were examined in the subicular complex, that is, the subiculum, presubiculum, and parasubiculum, of the adult mouse and were compared in detail with staining pattern of the acetylcholinesterase (AChE) histochemistry. In the parasubiculum, the overall immunostaining pattern of PV and calbindin were somewhat complementary. In the transition area calbindin-IR neurons were clustered but few PV-IR neurons were located, and thus the distribution of immunoreactive neuronal somata was apparently different from the adjacent parts of the parasubiculum, indicating that the transition area might be a separate entity.  

Other major sites of PTH/PTHrP receptor expression included the anterodorsal nucleus of the thalamus, basolateral amygdala, entorhinal cortex, parasubiculum, cells in the Purkinje cell layer of the cerebellum, vestibular nuclei, ventral cochlear nucleus, the motor nucleus of the trigeminal, and the facial and external cuneate nuclei.  

Because the parasubiculum (PaS) has extensive connections, either directly or indirectly, with these structures, it is centrally located to influence the neuronal activity in these areas.  

The sources of ipsilateral projections from the hippocampal formation, the presubiculum, area 29a-c, and parasubiculum to medial, orbital, and lateral prefrontal cortices were studied with retrograde tracers in 27 rhesus monkeys. Only a few labeled neurons were found in the parasubiculum, and most projected to medial prefrontal areas.  

These findings indicate a concerted discharge of the hippocampal and retrohippocampal cortices during SPW that includes neurons within CA3, CA1, and subiculum as well as neurons in layers V-VI of the presubiculum, parasubiculum, and entorhinal cortex.  

Projections from the retrosplenial granular area (RSG) to the retrohippocampal region terminate predominantly ipsilaterally in layers I, III, V and VI of the presubiculum, layers I and IV-VI of the parasubiculum, the molecular and pyramidal cell layers of the subiculum, and layers I, III, V and VI of the entorhinal area. On the other hand, projections from the retrosplenial agranular area (RSA) terminate predominantly ipsilaterally in layers I and III of the presubiculum and layers V and VI of the entorhinal and perirhinal areas, and ipsilaterally in layers IV-VI of the parasubiculum.  

The heavy PHA-L labeled fibers terminated in the stratum lacunosum and molecular of field CA1 of Ammon's horn of the hippocampus, and moderately in the subiculum, the presubiculum and the parasubiculum, mainly in the molecular layer.  

These cells were rare in the hippocampus and subiculum, but were more frequently observed in the presubiculum, parasubiculum, and in the entorhinal cortex. They were more frequent in the parasubiculum and entorhinal cortex.  

The non-CAnergic brain regions that represented CAT-stained cells were further divided into two groups: (i) regions containing AADC-labeled cells, for example, bed nucleus of the stria terminalis, nucleus suprachiasmaticus, mammillary body, nucleus raphe dorsalis, inferior colliculus, and nucleus parabrachialis, and (ii) regions containing no AADC-positive cells, for example, main olfactory bulb (except A16), accessory olfactory bulb, nucleus olfactorius anterior, caudoputamen, septum, nucleus accumbens, hippocampus, medial nucleus of the amygdala, entorhinal cortex, nucleus supraopticus, and parasubiculum.  

The relations between the inputs from the presubiculum and the parasubiculum and the cells in the entorhinal cortex that give rise to the perforant pathway have been studied in the rat at the light microscopical level. Projections from the presubiculum and the parasubiculum were labeled anterogradely, and, in the same animal, cells in the entorhinal cortex that project to the hippocampal formation were labeled by retrograde tracing and subsequent intracellular filling with Lucifer Yellow. The morphology of these projection neurons is highly variable and afferents from the presubiculum and the parasubiculum do not show a preference for any specific morphological cell type. In contrast, afferents from the parasubiculum form at least 2-3 times as many synapses on the dendrites of cells located in layer II than on neurons that have their cell bodies in layer III. Cells in layers I and IV of the entorhinal cortex receive weak inputs from the presubiculum and parasubiculum. Not only is the presubiculum different from the parasubiculum with respect to the distribution of projections to the entorhinal cortex, they also differ in their afferent and efferent connections. Therefore, we propose that the interactions of the entorhinal-hippocampal network with the presubiculum are different from those with the parasubiculum..  

The most rostral part of the AV projects to layers I and III of the ventral presubiculum, the pyramidal cell layer of the temporal subiculum, and deep layers of the parasubiculum and medial entorhinal area. The anterodorsal nucleus projects mainly to deep layers of the presubiculum, parasubiculum, and entorhinal area.  

In the subicular complex, chandelier cells were frequently stained in the parasubiculum, whereas only a few cells were found in the presubiculum.  

Zinc-containing neurons were observed in layers IV-VI of the medial entorhinal area, layers II and III of the parasubiculum, layers II, III and V of presubiculum, and in the superficial CA1 and deep CA3 pyramidal cell layers.  

The maximal density of sites was detected in the ventral and dorsal parts of the subiculum (115.0 +/- 3.4 and 87.0 +/- 2.8 fmol/mg proteins, respectively) and in the parasubiculum (100.1 +/- 5.4 fmol/mg proteins).  

The parasubiculum had a somewhat lower density of positive cells and fibers than the presubiculum.(ABSTRACT TRUNCATED AT 400 WORDS).  

Positive neurons were also conspicuous in the molecular layer of the dentate gyrus and in the pyramidal layer of CA3, sparse in the pyramidal layer of CA2 and CA1, and almost absent from presubiculum and parasubiculum.  

In rats, the subiculum and parasubiculum (layers II-III) were heavily labeled for beta 1-receptors; in contrast, guinea pigs had few receptors in these regions.  

The regional and laminar organization of the projections from the presubiculum and the parasubiculum to the entorhinal cortex was analyzed in the rat with the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L). The parasubiculum distributed projections not only to MEA but also to the lateral entorhinal area (LEA), innervating layer II selectively. Very weak projections from the parasubiculum to the contralateral entorhinal cortex were observed in this study. The position of the terminal plexus in the entorhinal cortex was determined by the point of origin along both the dorsoventral and transverse or proximodistal axes of the presubiculum and parasubiculum. Projections from the presubiculum and parasubiculum entered the entorhinal cortex at the level of the injection, or slightly ventral to it, and the main terminal field was always present ventrally to the injection site. The distribution in relation to the origin along the transverse axis was more complex, and differences between the presubiculum and parasubiculum were present. The distal part of the presubiculum, i.e., the part that borders the parasubiculum, projected to the central part of MEA. Projections from the portion of the parasubiculum directly adjacent to the presubiculum, the so-called proximal parasubiculum, reached medial parts of MEA, and those originating in the central part distributed preferentially to lateral parts of MEA and adjacent medial parts of LEA. The distal part of the parasubiculum that borders the entorhinal cortex projected mainly to almost the full mediolateral extent of LEA.(ABSTRACT TRUNCATED AT 400 WORDS).  

Other areas abundant in synapsin I mRNA were the layer II neurons of the piriform cortex and layer II and V neurons of the entorhinal cortex, the granule cell neurons of the dentate gyrus, the pyramidal neurons of hippocampal fields CA1 and CA2, and the cells of the parasubiculum.  

beta 4 mRNA was detected at high levels in the presubiculum, parasubiculum, subiculum and dentate gyrus of the hippocampal formation, in layer IV of the isocortex, in the medial habenula, in the interpeduncular nucleus, and in the trigeminal motor nerve nucleus.  

Specific hybridization occurred in neurons of the hilus of the dentate gyrus, fields CA1-3 in Ammon's horn, subiculum, presubiculum, parasubiculum and occasionally in neurons of the entorhinal cortex.  

The most pronounced reductions were found in CA2 and CA3, the subiculum, and the parasubiculum.  

The rostral part and the dorsalmost part of LD project densely to retrosplenial granular a (Rga) cortex, presubiculum and parasubiculum. In the postsubiculum the LD terminals are distributed to layers I and III/IV and extend into superficial layer V; in the presubiculum and the parasubiculum the LD terminals are only in the deep layers (i.e., layers IV-VI).  

The expression of NGF receptor-immunoreactivity increased within the subplate zone of the pre- and parasubiculum culminating in intense entorhinal cortex staining.  

In the forebrain, the c-kit mRNA signals were detected in the olfactory bulb, the caudate-putamen, throughout the superficial cortex, the accumbens nucleus, the nucleus of vertical limb diagonal band, the bed nucleus of anterior commissure, Ammon's horn, the entopeduncular nucleus, the subthalamic nucleus, the dorsal raphe nucleus, the parasubiculum, the presubiculum, the ventricular nucleus of lateral lemniscus, and the entorhinal cortex.  

Injections into the lateral mammillary nucleus revealed inputs from the presubiculum, parasubiculum, septal region, dorsal tegmental nucleus, dorsal raphe nucleus, and periaqueductal gray.  

High densities of receptor-associated silver grains were found in the olfactory bulb (internal plexiform layer), neocortex (layer III), nucleus accumbens, parasubiculum, subbrachial nucleus, parabigeminal nucleus, dorsal vagal complex, area postrema and the A2 region.  

In the parasubiculum, labeled cells were seen in layer II/III of the parasubiculum a and in layer V.  

The retrosplenial dysgranular cortex (Rdg) projects to the postsubiculum, caudal parts of parasubiculum, caudal and lateral parts of the entorhinal cortex, and the perirhinal cortex. The retrosplenial granular b cortex (Rgb) projects only to the postsubiculum, but the retrosplenial granular a cortex (Rga) projects to the postsubiculu, rostral presubiculum, parasubiculum, and caudal medial entorhinal cortex.  

The parasubiculum contained D1 receptors but not D2 receptors and the presubiculum had D2 receptors in layer 2 but few D1 receptors.  

The distribution of acetylcholinesterase (AChE) was examined in the multilayered posterior part of the hippocampal region of the adult mouse (Mus musculus domesticus), namely, the entorhinal area, the parasubiculum, the presubiculum, and those parts of the retrosplenial cortex that extend into the posterior hippocampal region (area retrosplenialis 29d and 29e). In the parasubiculum, a clear cytoarchitectural subdivision into a posterolateral parasubiculum a and an anteromedial parasubiculum b was observed.  

Additionally, neurofibrillary tangle-like argentophilic inclusions were consistently present in the gigantocellularis, reticularis, raphe and trapezoid nuclei, but rarely present in the dorsal and ventral subiculum, parasubiculum and anterior thalamus, and never found in the cerebral cortex, substantia nigra, locus ceruleus, or cerebellum.  

hippocampus, molecular layer (ipsilateral to lesion), entorhinal cortex (ipsilateral), dentate gyrus (ipsilateral), presubiculum (bilateral), parasubiculum (bilateral) and nucleus accumbens (bilateral).  

These projections differ from the thalamic projections to presubiculum and parasubiculum. These thalamic projections end in areas that are distinct from those to which the presubiculum and parasubiculum project. IV-VI), whereas presubiculum projects to layers I and III, and parasubiculum projects to layer II. These differences clearly mark the postsubiculum, the presubiculum, and the parasubiculum as distinct regions within the subicular cortex and suggest that they subserve different roles in the processing and integration of limbic system information..  

The cellular localization of transcripts for a new putative agonist-binding subunit of the neuronal nicotinic acetylcholine receptor (nAChR), alpha 5, was examined using in situ hybridization in the rat central nervous system (CNS), alpha 5 subunit mRNA was localized to a small number of regions when compared with two of the other known agonist-binding subunits, alpha 3 and alpha 4, alpha 5 mRNA is expressed at relatively high levels in neurons of the subiculum (pyramidal layer), presubiculum and parasubiculum (layers IV and VI), which are components of the hippocampal formation, in the substantia nigra pars compacta and ventral tegmental area, in the interpeduncular nucleus, and in the dorsal motor nucleus of the vagus nerve.  

The fibers carried by the cingulate bundle exclusively innervate field CA1 of the hippocampus, the dorsal part of the subiculum, and the presubiculum and parasubiculum.  

The present study describes the differences and similarities between the connections of the presubiculum and parasubiculum based on retrograde and anterograde tracing experiments. Both subicular areas also are innervated by axons originating in the ipsilateral and contralateral entorhinal cortex, presubiculum, and parasubiculum. Conversely, the parasubiculum is innervated primarily by axons that originate in area CA1 of the hippocampus, the basolateral nucleus of the amygdala, and the contralateral presubiculum and parasubiculum. The major efferent projection from the presubiculum and parasubiculum courses bilaterally to the medial entorhinal cortex; however, the results of the present study confirm previous suggestions that presubicular axons terminate almost exclusively in layers I and III, whereas parasubicular axons innervate layer II. The presubiculum also projects to the anteroventral and laterodorsal nuclei of the thalamus, and the lateral ventral portion of the medial mammillary nucleus, whereas the parasubiculum projects prominently to the anterodorsal nucleus of the thalamus, the contralateral presubiculum and parasubiculum, and the lateral dorsal segment of the medial mammillary nucleus. Thus despite some similarities, the major connections of presubiculum and parasubiculum are distinct from one another and distinct from the projections of the adjacent subiculum and postsubiculum.  

An occasional intensely stained multipolar NADPH-d containing neuron was observed in the subiculum, presubiculum and parasubiculum.  

They are also observed in the cellular islands within the molecular layer of the subiculum but not in the parasubiculum.  

A detailed description is given of the distribution of zinc in three areas of the domestic pig hippocampal region, viz., the entorhinal area, the parasubiculum, and the presubiculum. In the parasubiculum, the deep half of layer I together with layers II-III had the appearance of an intensely stained triangle wedged in between the entorhinal area and the presubiculum.  

Projections from the rostrodorsal and caudoventral subiculum terminated in a topographically organized laminar fashion in the medial mamillary nucleus bilaterally, whereas afferent projections from the presubiculum and parasubiculum terminated only in the lateral mamillary nucleus.  

The corresponding layer in the parasubiculum, in contrast, showed many neurofibrillary tangles and neuropil threads in the absence of amyloid.  

The Re projected axon terminals densely to the anterior cingulate cortex, infralimbic area of the medial frontal cortex, agranular insular cortex, entorhinal cortex, and parasubiculum.  

The lesions, which included entorhinal cortex, subiculum, pre- and parasubiculum and invaded the molecular layer of the dentate gyrus, completely eliminated the previously acquired conditional alternation learning, and performance failed to recover with 40 days of testing.  

The M2 receptor subtype was concentrated in the CA2 sector, the subiculum, the rhinal cortices, and the parasubiculum.  

The highest concentration of GnRH receptors is found in the parasubiculum. Injections of radioactive GnRH agonist Buserelin into the lateral ventricle results in selective and reversible labeling of the hippocampal areas CA1 through CA4 as well as the interpeduncular nucleus, central gray and the parasubiculum.  

As in the medial entorhinal area (EA), (K√∂hler, '86a) PHA-L injections restricted to individual layers of the lateral EA resulted in labeling of sparse projections to the subicular complex (e.g., subiculum, pre- and parasubiculum), whereas projections to the perirhinal area and piriform cortex were prominent. Whereas numerous axons appeared to terminate in layer 2, most fibers ascended into layer 1, where they ran in a medial direction, passing the medial EA, around the parasubiculum to the presubiculum.  

In contrast, in the Alzheimer disease hippocampal formation, the levels of amyloid-beta-protein mRNA in the cornu Ammonis field 3 and parasubiculum are equivalent.  

As well as primitive and classic plaques and AA, the beta protein immunostain demonstrated small deposits among the SP, small stellate deposits of layer 1, subpial fibrillar deposits, and focal cribriform deposits of parasubiculum, which may be new types of amyloid deposits.  

The subiculum, presubiculum, parasubiculum and entorhinal cortex were involved in all the cases.  

Following an injection into the pre- and parasubiculum, a large number of labeled cells were seen not only in the reuniens nucleus but in other midline nuclei. The pre- and parasubiculum receive projections from the most medial part of the reuniens nucleus near the midline, and the DLEA receives projections from the medial part of the nucleus.  

Medium binding densities were found in the parasubiculum and remaining layers of the entorhinal area and low densities occurred in the subiculum and in all subfields of Ammon's horn.  

Densest [ 3H]rauwolscine labeling appeared over nucleus caudate-putamen, nucleus accumbens, olfactory tubercle, Islands of Calleja, hippocampus, parasubiculum, basolateral amygdaloid nucleus and substantia nigra.  

The distribution of acetylcholinesterase (AChE) was examined in three areas of the hippocampal region of adult rabbit, viz., the entorhinal area, the parasubiculum, and the presubiculum. In the parasubiculum, layers I-III formed a wedge-shaped field with a very high content of AChE.  

High densities are found in the molecular layer of area dentata, all layers of regio superior and the subiculum, parasubiculum, and layers 2, and 4 through 6 of the entorhinal area.  

In the parasubiculum and EC longer lasting epileptiform events were observed which resembled seizure-like behaviour.  

Ammon's horn, dentate gyrus, subiculum, pre- and parasubiculum, lateral thalamic nucleus (intergeniculate leaflet), bed nucleus of the stria terminalis, medial preoptic area, lateral hypothalamus, mediobasal hypothalamus, supramammillary nucleus, pericentral and external nuclei of the inferior colliculus, interpeduncular nucleus, periaqueductal central gray, locus coeruleus, dorsal tegmental nucleus of Gudden, lateral superior olive, lateral reticular nucleus, medial longitudinal fasciculus, prepositus hypoglossal nucleus, nucleus of the solitary tract and spinal nucleus of the trigeminal nerve.  

The hippocampal regions in which the NPY-i neuron networks are most severely affected are the hilus, CA1, the parasubiculum, and the entorhinal cortex.  

The subicular complex is well endowed with cells and fibers and the parasubiculum consistently displays unusually heavy NPY innervation.  

Analysis of the PHA-L injections that were relatively well restricted to single layers of the MEA reveals very sparse projections to the parasubiculum, presubiculum, and subiculum, while numerous projections within the MEA are found.  

The subicular complex (e.g., the subiculum, pre-, and parasubiculum) and the entorhinal area contain fewer NPY-i cells than the rest of the hippocampal region. In the dorsal parts of the pre- and parasubiculum numerous small cells are scattered throughout all layers, while in the entorhinal area the NPY-stained cells are situated primarily in the deep layers (V and VI).  

Additional projections from the basal nuclei terminated in the prosubiculum, presubiculum, and parasubiculum.  

The absolute number of pyramidal cells (tissue volume X cell density) was diminished in CA1/CA2 (P less than 0.05), CA3 (P less than 0.05) and CA4 (P less than 0.05), but was not significantly changed in the prosubiculum/subiculum, the presubiculum/parasubiculum and the granular cell layer of the dentate fascia.  

In the rat most of the [ 3H]neurotensin binding was found in layer II of the medial entorhinal area and in the parasubiculum, while the lateral entorhinal area contained fewer [ 3H]neurotensin-binding sites. Binding sites for [ 3H]neurotensin were found also in the parasubiculum and in the molecular layer of the area dentata of the human brain.  

After iontophoretic injections of the lectin into the subiculum proper, presubiculum, or the parasubiculum, axons and terminal processes immunoreactive for PHA-L were traced to their respective terminal fields within the hippocampal region. Other retrohippocampal projections of the subiculum proper include the deep and the outer two layers of the presubiculum and the medial sector of the parasubiculum, in addition to a massive projection which terminates in the retrosplenial cortex. The fibers reach these layers via the deep layers of the MEA and through the molecular layer after first coursing around the parasubiculum. PHA-L injections into the parasubiculum labeled fibers that form a dense innervation of layer II in the MEA and the medial part of the lateral EA, and of the most medial sector of layer III in the MEA. Layer I and the superficial part of layer II of the contralateral MEA also contain a dense terminal network after PHA-L injections into the parasubiculum.(ABSTRACT TRUNCATED AT 400 WORDS).  

The pre- and parasubiculum contained a few positive axons.  

In the subiculum, pre- and parasubiculum the GAD and GABA-i cells were present in relatively large numbers in all layers, except the molecular layer, which contained only a small number of GABA cells. In the pre- and parasubiculum, on the other hand, the GABA cells were generally small to medium in size and morphologically more homogeneous than in the subiculum and entorhinal area.  

Moderate to low densities of binding was observed in layer III of the entorhinal area, the pre- and parasubiculum, the stratum pyramidale of the Ammon's horn, and the granular cell layer of the area dentata.  

Apparent terminal fields were also observed in superficial parts of the molecular layer, and deep parts of the pyramidal layer, of the subiculum, in the deepest layer of the presubiculum and parasubiculum, and in all layers of the entorhinal area..  

Incubations of horizontal sections through the hippocampus with [ 3H]spiperone (1 nM) resulted in dense labeling restricted to the pyramid cell layer in CA1, the parasubiculum and layers I and II of the entorhinal area (EA), while the other hippocampal subfields contained moderate to low binding.  

The parasubiculum projects to neither the contralateral entorhinal cortex nor the contralateral parasubiculum. The medial entorhinal cortex also gives rise to a minor projection to the contralateral parasubiculum and to the regio superior of the contralateral hippocampus and the caudalmost part of the outer molecular layer of the dentate gyrus.(ABSTRACT TRUNCATED AT 400 WORDS).  

Moderate receptor concentrations were found in the organum vasculosum of the lamina terminalis, median preoptic nucleus, medial habenular nucleus, lateral septum, ventroposterior thalamic nucleus, median eminence, medial geniculate nucleus, superior colliculus, subiculum, pre- and parasubiculum, and spinal trigeminal tract.  

After injection of radioactive amino acids into the cat thalamic centrum medianum, its projections have been revealed in the ipsilateral hemisphere in the frontal, motor, limbic, orbital and basal temporal cortex, in the parasubiculum and striatum.  

Microinjection of tetanus toxin into the limbic system structures (hippocamp, subiculum, presubiculum, parasubiculum) or chronic electric stimulation of these structures resulted in the formation of the generator of pathologically enhanced excitation (GPEE), followed by disturbances in the intraocular pressure regulation (IOPR).  

Analysis of serial horizontal and sagittal sections through the retrohippocampal region in colcicine-pretreated rats revealed a relatively large number of CCK-L immunoreactive cells in the pre- and parasubiculum, subiculum, and the medial and lateral entorhinal area (EA) at all dorsal to ventral levels of the region. The densest innervation was found in the parasubiculum, subiculum, and the ventrolateral entorhinal area.  

Of the 49 anatomically discrete regions examined, significant increases in glucose utilization were observed only in the hippocampus (stratum molecular lacunosum lacunosum and parasubiculum, increased by 16 and 17% respectively), the anterior nucleus of the thalamus (by 23%) and anterior cingulate cortex (by 30%).  

The serotonin (5-hydroxytryptamine; 5-HT) innervation of the retrohippocampal region (subiculum, pre- and parasubiculum, area 29e, medial and lateral entorhinal area) in the rat brain has been examined with antibodies against 5-HT used in combination with fluorescence histochemistry.  

2) the parasubiculum.  

While labeled cells were evident in layers II and III following injections into the reinnervated dentate gyrus, no labeled cells were found in the presubiculum or parasubiculum.  

Axonal projections are described from the lateral and basolateral nuclei of the amygdaloid complex, and from the overlying periamygdaloid and prepiriform cortices and the endopiriform nucleus, to the lateral entohinal area, the ventral part of the subiculum, and the parasubiculum in the cat and rat. The posterior division of the basolateral nucleus also projects to the posterodorsal part of the parasubiculum ("parasubiculum a" of Blackstad, '56).  

Thus, the precommissural fornix has been found to originate solely in fields CA1-3 of the hippocampus proper and from the subiculum; the projection to the anterior nuclear complex of the thalamus arises more posteriorly in the pre- and/or parasubiculum and the postsubicular area; the projection to the mammillary complex which comprises a major part of the descending columns of the fornix has its origin in the dorsal subiculum and the pre- and/or parasubiculum; and finally, the medial cortico-hypothalamic tract arises from the ventral subiculum. For example, all parts of fields CA1, CA2 and CA3 project to the subiculum, and at least some parts of these fields send fibers to the pre- and parasubiculum, and to the entorhinal perirhinal, retrosplenial and cingulate areas. From the region of the pre- and parasubiculum there is a projection to the entorhinal cortex and the parasubiculum of both sides. That part of the postsubiculum (= dorsal part of the presubiculum) which we have examined has been found to project to the cingulate and retrosplenial areas ipsilaterally, and to the entorhinal cortex and parasubiculum bilaterally..  

No labeled cells were found either in the presubiculum or parasubiculum following injections of the hippocampal formation. These cell populations were found capable of retrograde transport of HRP, however, since cells in both presubiculum and parasubiculum were labeled following HRP injections into the contralateral entorhinal area.  

Nor was convincing theta activity found in the subiculum, parasubiculum, presubiculum or entohinal areas..  

The fibers that are distributed by way of the fornix system to the hypothalamus (principally the arcuate-ventromedial region and the mammillary nuclei) and the anterior thalamus arise from the subicular region of the cerebral cortex (that is, the subiculum, presubiculum, and parasubiculum)..  


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