VGLUT1 and -2 expression is mostly segregated to specific divisions of the amygdale, with VGLUT2 being expressed only in the MEA, the anterior cortical nucleus (COAa), and the anterior basomedial nucleus (BMAa), whereas VGLUT1 is expressed in all other divisions of the amygdala. 
From the cortical nuclei, the most appreciable number of stained neurons was seen in the anterior cortical nucleus.
Using a rat brain slice preparation, we conducted whole-cell recordings on pyramidal neurons of the periamygdaloid cortex and the anterior cortical nucleus, two structures receiving direct connections from the olfactory bulb. Upon depolarization by current injection through the recording electrode, a fraction of periamygdaloid cortex and most anterior cortical nucleus layer II pyramidal neurons displayed an intermittent discharge pattern, where clusters of action potentials were interspersed by periods of membrane potential subthreshold oscillations.
Lighter projections to the posterior piriform cortex originated in the dorsolateral division of the lateral nucleus, the magnocellular and parvicellular divisions of the basal and accessory basal nuclei, and the anterior cortical nucleus.
As an initial step towards understanding the odor processing functions of these secondary olfactory structures, we recorded evoked field potentials in response to lateral olfactory tract stimulation in vivo in urethane-anesthetized Sprague-Dawley rats in the following brain structures: anterior olfactory nucleus, ventral and dorsal tenia tecta, olfactory tubercle, anterior and posterior piriform cortex, the anterior cortical nucleus of the amygdala, and lateral entorhinal cortex.
Dark and light neurons with morphological signs of secretory activity are described within one of the major sexually dimorphic zones of brain amygdaloid nucleus (anterior cortical nucleus).
The amygdalo-piriform transition area also projects moderately to other amygdaloid nuclei, including the parvicellular division of the basal nucleus, the anterior cortical nucleus, and the nucleus of the lateral olfactory tract.
This paper reports data on cytological peculiarities of neurons of two main zones of sexual dimorphism in brain amygdala (dorsomedial nucleus and anterior cortical nucleus).
Light projections were observed in the parvicellular division of the basal nucleus, the anterior cortical nucleus, the amygdalohippocampal area, and the anterior amygdaloid area.
In other amygdaloid nuclei, they were observed much less in the central nucleus, basomedial and anterior cortical nucleus.
Injections were also placed in the anterior cortical nucleus (COAa), a cell group superficially adjacent to the BMAa.
In addition, we examined connections of the anterior cortical nucleus and amygdalahippocampal area to determine whether portions of these nuclei should be included in the accessory basal nucleus (as some earlier studies suggest). Phaseolus vulgaris leucogglutinin was injected into different rostrocaudal levels of the accessory basal nucleus (n = 12) or into the anterior cortical nucleus (n = 3) or amygdalahippocampal area (n = 2). The projections originating in the anterior cortical nucleus and the lateral division of the amygdalohippocampal area differed from those originating in the accessory basal nucleus, which suggests that these areas are not part of the accessory basal nucleus.
The highest densities of the calretinin-immunoreactive neurons were observed in the anterior cortical nucleus, accessory basal nucleus, amygdalohippocampal area, and in the nucleus of the lateral olfactory tract.
The main intraamygdaloid targets of the basal nucleus projections are the nucleus of the lateral olfactory tract, the anterior amygdaloid area, the medial and capsular divisions of the central nucleus, the anterior cortical nucleus, and the amygdalohippocampal area.
The regions containing the lowest density of parvalbumin-immunoreactive cells were the paralaminar nucleus, the parvicellular division of the basal nucleus, the central nucleus, the medial nucleus and the anterior cortical nucleus.
In the anterior cortical nucleus, very few labeled cell bodies were found in the rostral pole, whereas they were abundant in the caudal quarter of the nucleus.
Anterograde tracers placed into the olfactory bulb labeled axons in eight primary olfactory cortical areas: the anterior olfactory nucleus, piriform cortex, ventral tenia tecta, olfactory tubercle, anterior cortical nucleus of the amygdala, periamygdaloid cortex, and olfactory division of the entorhinal cortex.
The regions containing the lowest densities of parvalbumin-positive profiles were the medial nucleus, anterior cortical nucleus, central nucleus, and the paralaminar nucleus.
The anterior cortical nucleus of the amygdala (COa) also projects to the dorsal part of the medial segment of MD and to its cortical targets, the medial orbital area (MO) and AIp.
Increased binding occurred in the anterior cortical nucleus of the amygdala in H animals.
Such cells were also found in additional forebrain regions that received direct efferent innervation from the main olfactory bulb, such as the anterior olfactory nucleus, two subdivisions of the olfactory amygdala (nucleus of the lateral olfactory tract and anterior cortical nucleus), and the cortical-amygdaloid transition zone.
In addition to the neuronal and fiber staining, a diffuse, blue neuropil staining was also observed, most commonly in the anterior cortical nucleus, the medial nucleus, the intercalated nuclei, and especially in the amygdalohippocampal area.
In agreement with this, injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) in the posterior half of the lateral hypothalamus labeled cells in four cortical areas that receive input from the olfactory bulb: the anterior olfactory nucleus, the piriform cortex (in the deepest layer or ventral endopiriform nucleus), the olfactory tubercle (in the deep polymorphic layer), and the anterior cortical nucleus of the amygdala. Injections of WGA-HRP in the anterolateral hypothalamus labeled cells only in the anterior cortical nucleus of the amygdala.
However, in the mouse neuronal labelling was observed throughout the neural axis, including cellular labelling in the bed nucleus of the anterior commissure, the median preoptic nucleus, the bed nucleus of the stria terminalis, the periventricular region, the anterior parvicellular subnucleus of the paraventricular nucleus, around the dorsomedial hypothalamic nucleus (pars compacta), the subincertal region, the arcuate nucleus, the anterior cortical nucleus of the amygdala, the suprageniculate nucleus, the lateral lemniscal nuclei, the lateraldorsal and lateralventral central gray, the posterior aspects of the commissural and marginal nuclei of the inferior colliculus, the paragenule nucleus, the A-5 region, the area postrema, the ventromedial nucleus of the solitary tract, area X, the spinal trigeminal nucleus (pars zonale), and superficial laminae of the spinal cord.
The main olfactory pathways have terminations in the posterolateral cortical nucleus (PLCN), and anterior cortical nucleus (ACN), both of which project to the PMCN and MN.
The infralimbic area does not project to the basolateral nucleus and cortico-amygdaloid projections from this area are focussed on the anterior cortical nucleus and the anterior amygdaloid area.
Type 1 receptors were concentrated in the anterior aspects of the amygdala, particularly the anterior cortical nucleus.
In addition, intracortical fibers from the anterior cortical nucleus of the amygdala are distributed throughout layer I, including layer Ia and Ib.
The anterior cortical nucleus projects to many parts of the olfactory cortex, but the fibers end in both superficial and deep parts of layer I (layer Ia and Ib).
As demonstrates the analysis of the data obtained, in male rats the following area respond to gonadectomy: neurons of the anterior amygdaloid area of the dep zone of the anterior cortical nucleus, of the central nucleus, of the posterior intercalated masses, of the dorsomedial nucleus, of the posterior medial nucleus and of the medial part in the posterior cortical nucleus.
As to the insular cortex, the posterior agranular insular area projects to all amygdaloid subdivisions; the BL, AC, and the anterior cortical nucleus (COa) receive, in addition, fibers from the ventral agranular area.
The association and commissural fiber systems arising in the olfactory cortical areas caudal to the olfactory peduncle (the piriform cortex, nucleus of the lateral olfactory tract, anterior cortical nucleus of the amygdala, periamygdaloid cortex and entorhinal cortex) have been studied utilizing horseradish peroxidase as both an anterograde and a retrograde axonal tracer. The nucleus of the lateral olfactory tract has a heavy bilateral projection to the medial part of the anterior piriform cortex and the lateral part of the olfactory tubercle (as well as a lighter projection to the olfactory bulb); both the anterior cortical nucleus of the amygdala and the periamygdaloid cortex project ipsilaterally to several olfactory cortical areas.
The anterior cortical amygdaloid nucleus and the prepiriform cortex both project to the infralimbic area and the ventral agranular insular area, and the anterior cortical nucleus also projects to the posterior agranular area and the perirhinal area.
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