Trochlear Nucleus

NPR-C immunoreactivity was detected in several regions, including the periaqueductal gray, oculomotor nucleus, red nucleus and trochlear nucleus of the midbrain; the pontine nucleus, dorsal tegmental nucleus, vestibular nucleus, locus coeruleus, trigeminal motor nucleus, nucleus of the trapezoid body, abducens nucleus and facial nucleus of the pons; and the dorsal motor nucleus of the vagus, hypoglossal nucleus, lateral reticular nucleus, nucleus ambiguus and inferior olivary nucleus of the medulla oblongata. Interestingly, NPR-C immunoreactivity was detected in the cholinergic neurons of the oculomotor nucleus, trochlear nucleus, dorsal tegmental nucleus, motor trigeminal nucleus, facial nucleus, dorsal motor nucleus of the vagus, nucleus ambiguus and hypoglossal nucleus.  

A high density of calcitonin gene-related peptide-immunoreactive perikarya was found in the superior colliculus, the dorsal nucleus of the raphe, the trochlear nucleus, the lateral division of the marginal nucleus of the brachium conjunctivum, the motor trigeminal nucleus, the facial nucleus, the pons reticular formation, the retrofacial nucleus, the rostral hypoglossal nucleus, and in the motor dorsal nucleus of the vagus, whereas a high density of fibers containing calcitonin gene-related peptide was observed in the lateral division of the marginal nucleus of the brachium conjunctivum, the parvocellular division of the alaminar spinal trigeminal nucleus, the external cuneate nucleus, the nucleus of the solitary tract, the laminar spinal trigeminal nucleus, and in the area postrema.  

In a previous study we have shown that the dendrites of oculomotor neurons form bundles which invade the trochlear nucleus, and vice versa, trochlear dendritic bundles invade the oculomotor nucleus.  

Consequently, we investigated these two likely intermediaries between the SC and trochlear nucleus electrophysiologically.  

The present study suggests that the principal sensory trigeminal nucleus projects to the bilateral ventromedial thalamic nucleus, periventricular pretectal nucleus, stratum album centrale of the optic tectum, caudomedial region of lateral preglomerular nucleus, ventrolateral nucleus of semicircular torus, medial part of rostral and posterior lateral valvular nucleus, oculomotor nucleus, trochlear nucleus, trigeminal motor nucleus, facial motor nucleus, superior and inferior reticular formation, descending trigeminal nucleus, medial funicular nucleus, inferior olive, and to the contralateral sensory trigeminal nucleus.  

Labeled terminals were also found bilaterally in the oculomotor nucleus, trochlear nucleus, trigeminal motor nucleus, facial motor nucleus, facial lobe, descending trigeminal nucleus, medial funicular nucleus, and contralateral sensory trigeminal nucleus and inferior olive. Labeled terminals in the oculomotor nucleus and trochlear nucleus showed similar densities on both sides of the brain.  

The overall identification of multiply-innervated muscle fiber and singly-innervated muscle fiber motoneurons within the rat oculomotor nucleus, trochlear nucleus, and abducens nucleus revealed that the smaller multiply-innervated muscle fiber motoneurons tend to lie separate from the larger diameter singly-innervated muscle fiber motoneurons.  

The MIF motoneurons lie around the periphery of the oculomotor nucleus (III), trochlear nucleus (IV), and abducens nucleus (VI), slightly separated from the SIF subgroups.  

The trochlear nucleus was located contralaterally and dorsolaterally adjacent to the fasciculus longitudinalis medialis in the mesencephalon.  

By comparison the trochlear nucleus and locus coeruleus form normally in ventral rhombomere 1 under these conditions.  

Galectin-1 mRNA was predominantly observed in the cell bodies of neurons such as oculomotor nucleus (III), trochlear nucleus (IV), trigeminal motor nucleus (V), abducens nucleus (VI), facial nucleus (VII), hypoglossal nucleus (XII), red nucleus, and locus ceruleus.  

A causal relation is unlikely since the most probable etiologies are either spontaneous discharges of trochlear nucleus neurons or a close contact between vessel and nerve analogously to trigeminal neuralgia..  

The biologically most significant difference between the mutations occurs in the oculomotor/trochlear nucleus which is affected in the pmn mouse but not in the wobbler and SOD G93A mice.  

Convergent neurons were further classified into vestibulospinal (n=28) and vestibulooculospinal (n=6) neurons by antidromic activation from the border between the C1 and C2 spinal cord and the oculomotor or trochlear nucleus.  

Immunoreactive elements were mainly localized to the spinal trigeminal, cuneate, solitary, vestibular, and cochlear sensory nuclei, dorsal motor nucleus of the vagus nerve, ventral grey column, hypoglossal nucleus, dorsal and ventrolateral medullary reticular formation, pontine subventricular grey and locus coeruleus, lateral regions of the rostral pontine tegmentum, tectal plate, trochlear nucleus, dorsal and median raphe nuclei, caudal and rostral linear nuclei, cuneiform nucleus, and substantia nigra.  

The peripheral neurons labeled from the lateral rectus muscle surround the medial half of the abducens nucleus: from superior oblique, they form a cap over the dorsal trochlear nucleus; from inferior oblique and superior rectus, they are scattered bilaterally around the midline, between the oculomotor nucleus; from both medial and inferior rectus, they lie mainly in the C-group, on the dorsomedial border of oculomotor nucleus.  

A few convergent neurons (3/12) projected to the oculomotor/trochlear nucleus.  

The trochlear nucleus appears in the posterior region of the basal plate of the midbrain at stage 13.  

Of these, 61 (43%) were antidromically activated by stimulation of the C1-C2 junction, 14 (10%) were antidromically activated by stimulation of the oculomotor or trochlear nucleus, and 14 (10%) were antidromically activated by stimulation of both the oculomotor or trochlear nucleus and the spinal cord.  

The contralateral pattern consisted of motoneurons innervating the superior rectus and the superior oblique that were located respectively in the caudal portion of the ventral oculomotor nucleus and in the trochlear nucleus.  

MRI documented contralateral tegmental lesions of the trochlear nucleus and adjacent intraaxial trochlear nerve.  

In the oculomotor-trochlear nucleus, beta-calcitonin gene-related peptide messenger RNA was the sole isotype expressed.  

The calibration was performed on the trochlear nucleus in developing chicks.  

The trochlear nucleus was located caudal to the oculomotor nucleus from which it was separated by a gap.  

In addition, in the brainstem, the oculomotor nucleus, trochlear nucleus, mecencephalic and motor nuclei of trigeminal nerve (N), abducens nucleus, facial nucleus, nucleus of the raphe pontis, dorsoral motor nucleus of vagal N, hypoglossal nucleus and ambiguus nucleus showed motopsin mRNA expression.  

It is likely that the lesion in our case affected the left MLF, the right trochlear nucleus or its fascicles and the left partial oculomotor fascicles.  

Neurons containing hybridization signal for ChAT mRNA were observed in the nucleus of the diagonal band of Broca, the basal nucleus of Meynert, the caudate nucleus, the putamen, the pedunculopontine tegmental nucleus, the laterodorsal tegmental nucleus, the parabigeminal nucleus, the oculomotor nucleus and the trochlear nucleus.  

those in the oculomotor nucleus, trochlear nucleus, motor trigeminal nucleus, facial nucleus and hypoglossal nucleus, are TBP-1 mRNA positive.  

In the midbrain, NAIP-LI was located primarily within neurons of the red nucleus, the substantia nigra pars compacta, the oculomotor nucleus, and the trochlear nucleus.  

Dense vascular net is found in the supratrochlear nucleus which lies in the central gray substance of the midbrain. Also, dense vascular net is noted within the red nucleus, trochlear nucleus, and the dorsal raphe nucleus.  

The highest levels of [ 3H]8-OH-DPAT binding were found in the ventrolateral subnucleus at the level of the caudal extent of the trochlear nucleus.  

MAP-2 immunoreactivity (IR) was significantly decreased in the CNS-lesioned trochlear nucleus, compared to the lesioned and the unlesioned trochlear nucleus of PNS-lesioned animals.  

The posterior commissure system gave rise to dense terminal fields in the contralateral NIC, the oculomotor nucleus, and the trochlear nucleus.  

Here, using the formation of the trochlear nucleus in the midbrain of duck embryos as a model system, we report that the floor plate and the notochord are not necessary for the development of these motor neurons in the brain stem.  

Fos-positive cells were predominantly located within the ventrolateral PAG region, extending from the level of the trochlear nucleus through the level of the caudal dorsal raphe.  

These cell groups are located in the dorsal telencephalic area, the inferior lobes of the hypothalamus, the pretectal area, the magnocellular superficial pretectal nucleus, the optic tectum, the oculomotor nucleus, the trochlear nucleus, the magnocellular vestibular nucleus, the secondary gustatory nucleus, the superior and medial reticular nuclei, the motor nucleus of the vagus and the ventral horn of the spinal cord.  

It is expressed in: (1) motor nuclei such as the oculomotor nucleus, trochlear nucleus, motor trigeminal nucleus, abducens nucleus, facial nucleus, ambiguus nucleus, dorsal motor nucleus of vagus and hypoglossal nucleus; (2) several sensory-related nuclei like the mesencephalic trigeminal nucleus, ventral nucleus of the lateral lemniscus, lateral and spinal vestibular nuclei, ventral and dorsal cochlear nuclei and nucleus of the trapezoid body; and (3) other regions such as the red nucleus, dorsal raphe nucleus, pontine nuclei, three cerebellar nuclei (medial, interposed and lateral), Purkinje cells, cells in the granular layer of the cerebellum, locus coeruleus, several areas of the reticular nucleus and area postrema..  

MLBNs projected to the trochlear nucleus as well through collateral branches of the axon projecting to the oculomotor nucleus.  

The distribution of neurons projecting to the trochlear nucleus of goldfish (Carassius auratus) was studied by the electrophoretic injection of horseradish peroxidase into the nucleus. The location of the injection site was electrophysiologically determined by the antidromic field potential elicited from the trochlear nucleus after the electrical stimulation of its nerve. These results are compared with the afferent sources to trochlear nucleus in mammals and with the set of structures projecting to the oculomotor and abducens nuclei in goldfish.  

The organization of the trochlear nucleus (N IV) was investigated in the frog Rana ridibunda. The present data give more insights into the organization of the N IV and demonstrate that, although the organization of the trochlear nucleus is highly conservative in gnathostome vertebrates, it shows specific features for each species studied, as demonstrated for amphibians..  

CGRP mRNA-expressing neurons were limited to the oculomotor and trochlear nucleus.  

The intense oxidase reactions were present in the red nucleus, oculomotor nucleus, trochlear nucleus, ventral nucleus of the lateral lemniscus, dorsal and ventral cochlear nuclei, vestibular nuclei, nuclei of posterior funiculus, nucleus of the spinal tract of the trigeminal nerve, lateral reticular nucleus, inferior olivary nucleus, and hypoglossal nucleus.  

The ChAT-positive neurons in PPNc are clustered along the dorsolateral border of the superior cerebellar peduncle (SP) at trochlear nucleus levels, whereas those in PPNd are scattered along the SP from midmesencephalic to midpontine levels. At levels caudal to the trochlear nucleus, ChAT-positive neurons corresponding to the laterodorsal tegmental nucleus (LDT) lie within the periaqueductal gray and extend caudally as far as locus coeruleus levels. Furthermore, at trochlear nucleus levels, about 40% of cholinergic neurons display glutamate immunoreactivity, whereas other neurons express glutamate or ChAT immunoreactivity only.  

Since other signs of oblique muscle palsy such as incomitance and cyclotropia were lacking or inappropriately slight, the author suggests the presence of a supranuclear lesion eliminating the vestibular input to the trochlear nucleus and to the subnucleus of the inferior oblique muscle while leaving the input for voluntary and visual gaze signals intact..  

Rotatory nystagmus has been rarely observed in the patients with MLF syndrome, and previous authors postulated a lesion in the MLF above the level of the abducens nucleus and below the level of the trochlear nucleus.  

Extensive analysis of all HRP retrogradely labelled material revealed no central fibre contribution to the IVth nerve other than from neurones resident in the trochlear nucleus. Ninety days after lesion, 10 +/- 4 (6% of control) neurones were labelled in the ipsilateral trochlear nucleus; none were labelled in the contralateral nucleus or in any other part of the midbrain, pons, medulla, or cerebellum.  

Following a unilateral section of the trochlear nerve, the effects of axotomy on cytochrome oxidase levels in the trochlear nucleus were studied.  

The ependyma covering the trochlear nucleus appears densely ciliated, differing from that of the classic circumventricular organs.  

The same pattern was observed when the trochlear nucleus was involved in the injection.  

Perineuronal nets were found in more than 100 brain regions, such as neocortex, hippocampus, piriform cortex, basal forebrain complex, dorsal lateral septal nucleus, lateral hypothalamic area, reticular thalamic nucleus, zona incerta, deep parts of superior and inferior colliculus, red nucleus, substantia nigra, some tegmental nuclei, cerebellar nuclei, dorsal raphe and cuneiform nuclei, central gray, trochlear nucleus, pontine and medullar reticular nuclei, superior olivary nucleus and vestibular nuclei.  

The rostral portion of the trochlear nucleus overlaps with the caudal pole of the ON.  

The trochlear nucleus exhibited the highest density of GABAergic terminations.  

A majority of the afferent input to the trochlear nucleus comes from the vestibular nuclei of the hindbrain via the medial longitudinal fasciculus.  

Labeled cuneiform and midline cells, on the other hand, were quite numerous, extending both from a level just caudal to the trochlear nucleus to levels far beyond the rostral tip of the somatic oculomotor nucleus.  

The trochlear nucleus (M IV) is located caudally, distinct from M III, and projects predominantly to contralateral eye muscles with a ratio of 6:1 (18:3 neurons).  

This hypothesis was tested by recording the activity of 31 neurons in the trochlear nucleus, which contains the superior oblique motoneurons.  

After SR and SO injections labeled cells were found in the bilateral oculomotor nucleus and the bilateral trochlear nucleus, respectively, predominantly on the contralateral side.  

It proved impossible to identify the boundary between the oculomotor nucleus and trochlear nucleus in the coronal sections so that in such sections the combined total of neurons in both nuclei was estimated. The trochlear nucleus was intact in all but one of the sets of sagittal sections and trochlear neuron number was estimated separately in eleven brains.  

The central processes of type Aa neurons projected to the following three groups of target nuclei: 1) nuclei functioning as interneurons, including supratrigeminal nucleus (Vsup), intertrigeminal nucleus (Vint), juxta-trigeminal region (Vjux), and parvicellular nucleus of the pontomedullary reticular formation (PcRF); 2) motor nuclei, including the trigeminal motor nucleus (Vmo), accessory facial nucleus (NVIIacs), accessory abducens nucleus (NVIacs), and a small number of labeled axons in the oculomotor nucleus and trochlear nucleus; 3) sensory nuclei, including the dorsomedial part of the principal trigeminal sensory nucleus (Vpdm) and the dorsomedial part of subnucleus oralis of the trigeminal spinal nucleus (Vodm).  

After injection of the trochlear nucleus, labelled neurons were found in the ipsilateral superior nucleus and contralateral medial and descending nuclei: a few labelled cells were also observed in the ipsilateral medial and descending nuclei as well as in the contralateral cell group Y..  

Unilateral labelling of the ascending medial longitudinal fascicle (MLF), just caudal to the trochlear nucleus, labelled coherent groups of vestibular neurons that had an asymmetrical distribution on the two sides of the brainstem.  

Axons of downward VMLBs ramify ipsilaterally in the inferior rectus portion of the oculomotor nucleus and in the trochlear nucleus.  

Extracellular field potentials recorded within the trochlear nucleus and/or the inferior rectus subdivision of the oculomotor nucleus were averaged by the use of spike potentials of single DPV neurons as triggers. All the crossed-DPV axons tested induced negative unitary field potentials in the trochlear nucleus (n = 9) and in the inferior rectus subdivision of the oculomotor nucleus (n = 5), suggesting that they made monosynaptic excitatory connection with motoneurons in these nuclei. The uncrossed-DPV axons did not induce such unitary field potentials either in the trochlear nucleus (n = 4) or in the inferior rectus subdivision (n = 3). All these axons ascended in the MLF contralateral to their soma, gave off many collaterals to the trochlear nucleus, and projected more rostrally.  

Single-unit recordings were made in the medial longitudinal fasciculus (MLF) near the trochlear nucleus from axons that were monosynaptically activated after electrical stimulation of the vestibular nerve.  

indicated that at least some of the looping fibres observed within the lesioned AMVs originated in the ipsilateral trochlear nucleus.  

Neurons were also labelled in the prepositus nucleus after injection of HRP in the trochlear nucleus.  

There were no terminations in the trochlear nucleus even though 12 labeled fibers passed close to it.(ABSTRACT TRUNCATED AT 400 WORDS).  

Two main visual pathways can be recognized: The first projects from the retina to the parvicellular nucleus, and then to the intermediate nucleus of the superficial pretectum, the inferior raphe nucleus, and the trochlear nucleus.  

Vestibular neurons that project to the trochlear nucleus were studied following unilateral injections of horseradish peroxidase. After injections centered on the trochlear nucleus, one-third of the labeled neurons were located in the ipsilateral superior (S) vestibular nucleus and almost half were in the contralateral medial (M) vestibular nucleus.  

Area B nInt projects to the ipsilateral spinal cord, contralateral nInt, pretectal nucleus lentiformis mesencephali, and ipsilateral trochlear nucleus.  

With colchicine treatment, calcitonin gene-related peptide-like immunoreactive cells were found in more areas of the brain stem such as the abducens nucleus, parabigeminal nucleus, principal oculomotor nucleus, trochlear nucleus and central gray, along with the nuclei which had shown calcitonin gene-related peptide immunoreactivity in the untreated animals.  

Injections of WGA-HRP into the corpus resulted in retrograde labeling of the following cell groups bilaterally: pretectal and accessory optic nuclei, interstitial nucleus of Cajal, nucleus ruber, oculomotor and possibly trochlear nucleus, central (periaqueductal) gray, nucleus H, reticular formation of the midbrain, cerebellar nucleus, caudal part of nucleus F, tentatively locus coeruleus and subcoeruleus field, octaval and trigeminal nuclei, intermediate octavolateralis nucleus, medial inferior reticular formation, lateral reticular nucleus, and spinal cord.  

The trochlear nucleus, which rostrally overlaps the oculomotor nuclear complex, is for the greater part a comma-shaped cell group situated lateral, dorsal, and medial to the medial longitudinal fasciculus.  

The oculomotor nucleus emits nerve fibres, as does also the trochlear nucleus, which lies in the isthmic segment.  

The labelled cells for the superior oblique muscle were found in the contralateral trochlear nucleus and those for the lateral rectus muscle bilaterally in the abducens nuclei, predominantly on the ipsilateral side and poorly on the contralateral side.  

Neurons in the rostromedial portions of the complex project to the contralateral trochlear nucleus.  

In the mesencephalon, motoneurons of the oculomotor and trochlear nucleus, as well as neurons within the pedunculopontine tegmental nucleus and the red nucleus were Chol-1-positive.  

Rostral stem axons could be traced to the level of the trochlear nucleus and inferior to the medial longitudinal fasciculus.  

The oculomotor nucleus is situated ventral to the posterior pole of the magnocellular mesencephalic nucleus and the trochlear nucleus is found caudal and dorsal to this. The majority of extraocular motoneurons have piriform perikarya and long beaded dendrites that extend laterally in the oculomotor and abducens nuclei and rostrally in the trochlear nucleus.  

They had axons that crossed the midline and ascended in the medial longitudinal fasciculus (MLF) to terminate in the trochlear nucleus, the lateral aspect of the caudal oculomotor nucleus, and the dorsal aspect of the rostral oculomotor nucleus.  

Most motoneurons of the trochlear nucleus projected to the contralateral superior oblique muscle although a small number innervated the ipsilateral superior oblique.  

The quantitative and qualitative development of the trochlear nucleus of salamanders and frogs was studied using horseradish peroxidase (HRP) as a retrograde marker. Many more labelled trochlear motoneurons were found in adult than in larval amphibians, and [ 3H]thymidine labelling showed postlarval cell production in the area of the trochlear nucleus.  

A medium amount of degenerated terminals were observed in the nucleus pretectalis anterior (pars reticularis), the dorsal part of the periaqueductal grey at its most rostral levels, the caudolateral parts of the nucleus pretectalis posterior and the nucleus of optic tract, the H field of Forel, parts of the somatic cell columns of the oculomotor nucleus and the trochlear nucleus. Following an HRP (dissolved in 5% alkyl-phenol ethylene oxide) injection into the unilateral area pretectalis where fibers of the posterior commissure fan out, retrogradely labeled cells were observed in all of the above described (posterior commissural fiber recipient) regions of the pretectal and neighboring structures, with the exception of the somatic cell columns of the oculomotor nucleus and the trochlear nucleus.  

Extraocular muscle motoneurones were localised in the oculomotor nucleus (ON), trochlear nucleus (TN) and abducens nucleus (AN) in the marmoset brain using the horseradish peroxidase (HRP) retrograde labelling technique.  

The different clusters appeared to constitute parts of a coherent structure which is located between 3-5 mm lateral to the midline at the anterior/posterior level of the trochlear nucleus, and with slanted dorsal-ventral distribution with the caudal parts above and the rostral parts below the Sylvian aqueduct.  

The trochlear nucleus of the rabbit has not been previously studied by methods of axonal transport. The trochlear nucleus contains approximately 900 neurons; most are motoneurons the axons of which travel in the trochlear nerve and decussate in the anterior medullary velum.  

Injection of the non-toxic fragment C of tetanus toxin into the superior oblique muscle of the eye results in strong direct retrograde labelling of the motoneurons in the contralateral trochlear nucleus and clear transsynaptic labelling of neurons in the ipsilateral and contralateral vestibular nuclei. Moreover, a fragment C injection into the superior oblique muscle labels transsynaptically more neurons in each vestibular nucleus than an injection of HRP into the trochlear nucleus labels directly..  

The influence of innervation on the initial differentiation of muscle fibre types was investigated by using the trochlear nucleus-superior oblique muscle system of duck.  

Intracellular techniques were used to study single motor units of the trochlear nucleus and superior oblique muscle in the cat.  

Other, less extensive, termination sites of both neuron classes were in the contralateral vestibular nuclear complex, the facial nucleus, the medullary and pontine reticular formation, midline areas within and neighboring the raphé nuclei, and the trochlear nucleus. Typical for posterior canal neurons, the major termination sites were in the trochlear nucleus (superior oblique motoneurons) and in the inferior rectus subdivision of the oculomotor nucleus. The axons of ipsilaterally projecting neurons ascended through the reticular formation to join the MLF caudal to the trochlear nucleus. The main target sites of anterior canal related neurons were in the trochlear nucleus and the inferior rectus subdivision of the oculomotor nucleus.  

Although almost all labeled neurons were on the contralateral trochlear nucleus about 5% of them and their axons were on the ipsilateral side. These findings confirmed that the superior oblique muscle was innervated partially by a small number of ipsilateral trochlear nucleus..  

Major termination sites were in the trochlear nucleus and in the inferior rectus subdivision of the oculomotor nucleus.  

The trochlear nucleus, containing superior oblique motor neurons, was found in the immediate lateral and caudal neighborhood of the oculomotor nucleus, where its rostral border overlapped with the caudal border of the latter.  

The present study was undertaken to examine the development of the trochlear nucleus in quail and to compare the mature trochlear nucleus, nerve, and their sole target of innervation, the superior oblique muscle, in quail, chick, and duck. Study of the trochlear nucleus in quail from embryonic day 5 through hatching shows a maximum of 1,248 neurons on embryonic day 10 followed by spontaneous degeneration of 40% of the neurons between days 10 and 16.  

SVN projects via the medial longitudinal fasciculus (MLF) to the ipsilateral trochlear nucleus (TN), the inferior rectus subdivision of the OMC, the INC, the nucleus of Darkschewitsch (ND) and the rostral interstitial nucleus of the MLF (RiMLF).  

This study investigated the nature of synaptic inputs from the Forel's field H (FFH) in the medial mesodiencephalic junction to inferior oblique (IO) motoneurons in the oculomotor nucleus and superior oblique (SO) motoneurons in the trochlear nucleus in anesthetized cats, using intracellular recording techniques.  

Counts of HRP filled neurons in the trochlear nucleus after injection of the superior oblique muscle showed that axons entering the IVth nerve rootlet were exclusively ipsilateral trochlear fibres.  

Inputs to these cells were tested by stimulating the medial longitudinal fasciculus (MLF) 5 to 6 mm rostral to the obex, the lateral vestibular nucleus (LVN), the upper MLF 1 mm caudal to the trochlear nucleus, and the medial vestibular nucleus (MVN), all on the ipsilateral side.  

In some cases the condition may be due to abnormal discharges from the affected trochlear nucleus..  

Ascending projections from NGC to the motor nucleus of V, trochlear nucleus, oculomotor nucleus, Edinger-Westphal nucleus, the ventral aspect of the periaqueductal gray, the deep and intermediate layers of the superior colliculus, nucleus parafasicularis and centromedianus, the Fields of Forel and the dorsal and lateral hypothalamic nuclei were observed.  

Contralateral structures associated with ascending vestibulo-ocular pathways which contained heavy labeling were the medial longitudinal fasciculus, abducens nucleus, trochlear nucleus, and two parts of the oculomotor nucleus--the dorsolateral part and the ventromedial part. Less heavily labeled ipsilateral vestibulo-ocular-related structures included the medial longitudinal fasciculus, abducens nucleus and the ventrolateral edge of the trochlear nucleus.  

Efferent projections of MVN are to: (1) the ipsilateral supraspinal nucleus (SSN), and (2) the contralateral central cervical nucleus (CCN), MVN, SVN, cell group 'y', the rostroventral region of LVN, the trochlear nucleus (TN) and the INC.  

Individual vestibuloocular neurons activated by stimulation of the ampullary nerve of the anterior semicircular canal (ACN) inhibited motoneurons in both the ipsilateral (i-) trochlear nucleus and i-inferior rectus motoneuron pools.  

Effects of sera or immunoglobulins from patients with acquired myasthenia gravis on motor neuron survival during critical stages of embryonic development were investigated in the trochlear nucleus-superior oblique muscle system of white Peking duck embryos.  

The ascending branches gave rise to collaterals that terminated in both the trochlear nucleus and the inferior rectus subdivision of the oculomotor nucleus.  

Individual vestibuloocular neurons receiving input from the ampullary nerve of the posterior semicircular canal excited motoneurons in both the contralateral trochlear nucleus and contralateral inferior rectus motoneuron pools.  

The naturally occurring nerve cell death in the trochlear nucleus and some other motor cranial nerve nuclei has been prevented after postsynaptic blockade with alpha-BTX or dTC, but an increased cell death has been found after presynaptic blockade with beta-BTX.  

A dose of 0.004 mg of reserpine produced the suppression, but had no deleterious effects, in terms of embryonic survival or in long-lasting changes in cell numbers, as reflected by cell counts in the trochlear nucleus, a population which was undergoing proliferation at the time of reserpine injection.  

Injection of HRP into the superior oblique, superior rectus or medial rectus muscle produced labeling of motoneurons in the corresponding subdivisions of the oculomotor nucleus or trochlear nucleus but no labeled motoneurons were observed in either the ABD or ACC nuclei.  

The cytoarchitecture of the oculomotor nuclear complex (ONC) and of the trochlear nucleus (TN) was studied in the encephalon of 10 adult marmosets (Callithrix jacchus). The trochlear nucleus of the marmoset is compact, round in shape and can be divided in to central cellular, dorsoventral and ventrolateral groups.  

The majority of vestibulo-ocular neurons projecting to the inferior rectus motoneuron pool in the contralateral oculomotor nucleus was activated antidromically from the contralateral trochlear nucleus as well.  

The motoneurons of the superior oblique are located in the contralateral trochlear nucleus although a few labeled neurons were scattered laterally in amongst the fibers of the medial longitudinal fasciculus.  

Unilateral injections of the oculomotor complex which included the trochlear nucleus resulted in retrograde labeling of small cells within the ipsilateral nBORd and predominantly medium and large cells in the contralateral nBOR.  

Cell counts of the trochlear nucleus on day 19 indicate a mean increase of 37% (range 19--62%) in the number of cells on the experimental side (contralateral to the graft) as compared to the ipsilateral control nucleus of the same embryos.  

This nucleus has direct bilateral axonal projections onto the oculomotor nuclear complex, the trochlear nucleus- and folia IXc,d and paraflocculus of the vestibulocerebellum.  

The superior colliculus projects lightly to a cell group directly ventrolateral to the trochlear nucleus.  

The medial longitudinal fasciculus (MLF) and immediately adjacent reticular formation were stimulated electrically just caudal to the trochlear nucleus in the cat.  

Three cases showed an increase in the number of cells in the trochlear nucleus ranging from 9 to 29%.  

Assuming all cells send their axons into the nerve and that all cell bodies are present within the trochlear nucleus, the ration of cells to fibers is 1:20.  

Fibres coming from the trochlear nucleus might correspond to collaterals of motor axons..  

Following intravitreal injections, retrograde transport of the enzyme was observed bilaterally, but predominantly contralaterally, in a large oblong field of cells at the isthmic level of the midbrain, bounded medially by the trochlear nucleus and laterally by the nucleus isthmi.  

Ultrastructural degeneration studies were carried out on the cat trochlear nucleus following lesion of the vestibulo-trochlear pathway in order to characterize the location and type of presynaptic endings involved in this pathway. Four types of boutons are found in the normal trochlear nucleus. Following the interruption of the ascending projection from the ipsilateral superior and medial vestibular nuclei by parasagittal medullary lesions, degeneration of Type II boutons was commonly encountered in the ipsilateral trochlear nucleus. Predominantly Type III degeneration was found in the contralateral trochlear nucleus. Electrical stimulation of the vestibular nerve showed that these lesions resulted in (1) a complete loss of inhibition in the ipsilateral trochlear nucleus and (2) a significant (75-90%) reduction in the contralateral excitatory pathway to the trochlear nucleus.  

Extracellular recordings were obtained from 37 histologically identified MLF fibers near the trochlear nucleus in alert monkeys trained to perform a visual tracking task and subjected to adequate horizontal and vertical vestibular stimulation.  

Twelve to 14 days following lesions of the ipsilateral superior vestibular nucleus or its efferent pathway to the oculomotor and trochlear nuclei, at a time when there is extensive degeneration of superior vestibular nucleus axon terminals in these nuclei, the synthesis and storage of GABA in the ipsilateral trochlear nucleus is markedly reduced compared to that in the contralateral trochlear nucleus; the synthesis of acetylcholine, dopamine and tyramine is not measurably affected. The data support the identity of GABA as an inhibitory transmitter in the superior vestibular nucleus-trochlear nucleus pathway..  

In lizards (Sceloporus undulatus), long term (13 or 19 weeks) acclimation to an environment of 6 degrees C produces a striking increase in the argyrophilic neurofibrillar network in most large perikarya of the trochlear nucleus.  

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