Posterior Cortical Nucleus Research Articles

The brain of the tree pangolin (Manis tricuspis). VII. The amygdaloid body.

Here, we describe the cytoarchitecture and chemoarchitecture of the amygdaloid body of the tree pangolin. Our definition of the amygdaloid body includes the pallial portions of the amygdala, and the centromedial group that is a derivative of the subpallium and part of the extended amygdala. The remainder of the extended amygdala is not described herein. Within the amygdaloid body of the tree pangolin, we identified the basolateral group (composed of the lateral, basal, and accessory basal amygdaloid nuclei), the superficial, or cortical nuclei (the anterior and posterior cortical nuclei, the periamygdaloid cortex, and nuclei of the olfactory tract), the centromedial group (the central amygdaloid nucleus and the medial nuclear cluster), and other amygdaloid nuclei (the anterior amygdaloid area, the amygdalohippocampal area, the intramedullary group, and intercalated islands). The location within and relative to each other within the amygdaloid body and the internal subdivisions of these groups were very similar to that reported in other mammalian species, with no clearly derived features specific to the tree pangolin. The only variation was the lack of an insular appearance of the intercalated islands, which in the tree pangolin were observed as a continuous band of neurons located dorsomedial to the basolateral group similar in appearance to and almost continuous with the intramedullary group. In carnivores, the closest relatives of the pangolins, and laboratory rats, a similar appearance of portions of the intercalated islands has been noted.

Nuclear organization of the African elephant (Loxodonta africana) amygdaloid complex: an unusual mammalian amygdala.

Here we describe the nuclear organization of the African elephant amygdaloid complex using Nissl, myelin, and a range of immunohistochemical stains. The African elephant is thought to exhibit many affect-laden and social-empathic behaviours; however, to date the amygdaloid complex, which is the generator of emotional states of the brain is yet to be fully explored in the elephants. For the most part, the amygdaloid complex of the African elephant is similar to that observed in other mammals in terms of the presence of nuclei and their topological relationships; however, we did observe several specific differences in amygdaloid organization. The elephant amygdala has undergone rotation in both the coronal and sagittal planes, seemingly associated with the expansion of the temporal lobe. Numerous scalloped cell clusters, termed glomeruli, forming the intermediate nuclei of the basal, accessory basal and central nuclear groups, were occupied by structures immunopositive to doublecortin. The nuclei typically associated with the accessory olfactory system (posterior cortical nucleus and medial nuclear complex) were absent from the elephant amygdala. The anterior cortical nucleus is very large and appears to be comprised of two subdivisions. The lateral nuclear complex is expanded and has two novel subdivisions. The amygdalohippocampal area appears relatively enlarged. The numerous shared and derived characters make the elephant amygdaloid complex very unusual and unique amongst mammals, but the derived characters appear to relate to observed elephant affect-laden behaviours.

Robust age, but limited sex, differences in mu-opioid receptors in the rat brain: relevance for reward and drug-seeking behaviors in juveniles

In the brain, the µ-opioid receptor (MOR) is involved in reward-seeking behaviors and plays a pivotal role in the mediation of opioid use disorders. Furthermore, reward-seeking behaviors and susceptibility to opioid addiction are particularly evident during the juvenile period, with a higher incidence of opioid use in males and higher sensitivity to opioids in females. Despite these age and sex differences in MOR-mediated behaviors, little is known regarding potential age and sex differences in the expression of MORs in the brain. Here, we used receptor autoradiography to compare MOR binding densities between juvenile and adult male and female rats. Age differences were found in MOR binding density in 12 out of 33 brain regions analyzed, with 11 regions showing higher MOR binding density in juveniles than in adults. These include the lateral septum, as well as sub-regions of the bed nucleus of the stria terminalis, hippocampus, and thalamus. Sex differences in MOR binding density were observed in only two brain regions, namely, the lateral septum (higher in males) and the posterior cortical nucleus of the amygdala (higher in females). Overall, these findings provide an important foundation for the generation of hypotheses regarding differential functional roles of MOR activation in juveniles versus adults. Specifically, we discuss the possibility that higher MOR binding densities in juveniles may allow for higher MOR activation, which could facilitate behaviors that are heightened during the juvenile period, such as reward and drug-seeking behaviors.

Paleoamygdala: The morphogenesis of nuclear-type, paleocortical and intermediate formations in the period of postnatal development in rats

The cytoarchitectonics and expression of apoptosis (as an indicator of stabilization of formative processes) in nuclear, paleocortical, and intermediate formations of the paleoamygdala of the rat ondays 21, 24, 28, and 31 of postnatal development was studied. The results of analysis suggest that the morphogenesis of these formations is characterized by heterochrony due to the complexity of their structural organization predefined by the phylogenetic age. On day 21 of postnatal development of the rat, only the dorsomedial nucleus is well differentiated; on days 24-28, the posterior medial nucleus is well differentiated. The medial part of the posterior cortical nucleus (intermediate formation) is differentiated from the lateral part of this nucleus on day 28. The lateral part of the posterior cortical nucleus, which exhibits the characteristics of a paleocortical formation, acquires the cytoarchitectonics characteristic of an adult animal on day 31 of postnatal development. The dynamics of changes in the apoptotic index reflects the stabilization of morphogenetic processes characterized on the basis of cytoarchitectonic criteria. The results of this study and the neurogenetic data, indicating the presence of spatiotemporal gradients in the formation of the amygdaloid complex and the multiplicity of the original histogenetic domains, confirm the correctness of the previous concept (Akmaev and Kalimullina, 1993) on the substrate of this brain structure as a nuclear-paleocortical component of the brain.

Paleoamygdala: Morphogenesis of the Posterior Cortical Nucleus of the Rat Amygdaloid Complex of the Brain during the Early Juvenile Period

Sex-related differences and the dynamic of formation of the posterior cortical nucleus of the rat amygdaloid complex were revealed in the early juvenile period by planimetric characteristics, numbers of neurons and glial cells, and glial and apoptotic indexes reflecting morphological restructuring on postnatal days 21, 24, 28, and 31.

The Paleoamygdala: Comparative Analysis of Its Structural-Functional Organization in WAG/Rij and Wistar Rats

Light microscopy (Nissl staining, computerized morphometric analysis), electron microscopy (using criteria for assessment of the functional state of neurons), and the TUNEL method for identifying apoptotic cells were used to undertake a comparative analysis of the structural-functional organization of the paleoamygdala. The results of this analysis suggested that limbic brain structures are involved in the pathogenesis of absence epilepsy. The area occupied by the amygdaloid body on sections was significantly greater in WAG/Rij rats (a model of absence epilepsy). Assessment of the ultrastructural characteristics of neurons in all paleoamygdala structures (the dorsomedial, posterior medial, and posterior cortical nuclei) in WAG/Rij rats identified decreases in their functional activity. In addition, WAG/Rij rats showed an increased number of pyknomorphic neurons with signs of apoptosis identified by the TUNEL method, pointing to destructive processes.

Sex-specific expression of estrogen receptors α and β and Kiss1 in the postnatal rat amygdala.

The rodent amygdaloid complex is composed of numerous subnuclei important for the sex-specific regulation of sociosexual behavior. Although estrogen receptors (ERs) are critical for organizing functional and cytoarchitectural sex differences in these subnuclei, a detailed developmental profile of ER expression in the amygdaloid complex is not available. Moreover, the kisspeptin gene (Kiss1) was recently identified in the adult amygdala, but it remains unknown if it is expressed during development. To fill these data gaps, rat brains (5-7/group) were assessed on postnatal days (PNDs) 0, 2, 4, 7, and 19 for ER alpha (ERα; Esr1), beta (ERβ; Esr2), and Kiss1 expression using in situ hybridization. Expression was quantified in the posterodorsal portion of the medial amygdala posterodorsal (MePD), lateral (PLCo), and medial (PMCo) components of the posterior cortical nucleus, and the amygdalohippocampal area (AHi). ERα expression was high throughout the amygdala at birth, but sexually dimorphic only in the AHi. ERα expression in the MePD and the PLCo showed a U-shaped expression pattern over time. In the PMCo, ERα expression decreased from PND 2 and remained low through PND 19. Sexually dimorphic expression of ERβ in the MePD was observed on PND 0, with higher levels in females, but reversed by PND 4 due to declining levels in females. No Kiss1 signal was observed in the postnatal amygdala, suggesting that expression arises after puberty. These data reveal that ER expression is region-specific within the neonatal amygdala. These differences likely contribute to sex differences in sociosexual behavior across the lifespan.

Regionally specific increased volume of the amygdala in Williams syndrome: Evidence from surface‐based modeling

Williams syndrome (WS) is a condition caused by a contiguous deletion of approximately 26-28 genes from chromosome 7, and is characterized by abnormal social and emotional processing and abnormal structure and function of the amygdala. Prior studies show that the amygdala is relatively enlarged in WS, but very little is known regarding the regional specificity of increased amygdalar volume in this condition. Here we investigated the regional specificity of structural alterations of the amygdala in WS, compared to a typically developing (TD) control group. We acquired high resolution brain MRI data from 79 participants (39 WS, 40 TD) and used a surface-based analytical modeling approach. The WS group exhibited several areas of increased radial expansion of the amygdalar surface and no areas of decreased radial expansion of the amygdalar surface compared to TD controls. The areas found to exhibit particularly increased radial expansion in WS included the bilateral posterior cortical nucleus, lateral nucleus, and the central nucleus. This greater regional and anatomical specificity of altered amygdala structure in WS contributes to a model relating genetic risk in WS to the development of key brain regions for social and emotional functioning.

Pancreatitis-associated protein-I and pancreatitis-associated protein-III expression in a rat model of kainic acid-induced seizure

The pancreatitis-associated protein (PAP) family (also known as the regenerating gene (Reg) family) is a group of 16 kDa secretory proteins structurally classified as the calcium dependent-type lectin superfamily. Some PAP family members are expressed in neurons following peripheral nerve injury and traumatic brain injury. To determine whether PAP family members are expressed in non-traumatic brain injury, expressions were analyzed following kainic acid (KA)-induced seizure. PAP-I (also known as Reg2 in rat and RegIII-beta in mouse) and pancreatitis associated protein-III (PAP-III; RegIII-gamma in mouse) messenger ribonucleic acid (mRNA) was transiently expressed in some restricted areas, such as the hippocampus and parahippocampal area; expression was observed immediately at a maximal level 1 day after seizure. Expression disappeared within 3 days after seizure. In situ hybridization (ISH) and immunohistochemistry revealed neuronal PAP-I and PAP-III expression in the hippocampal dentate gyrus, perirhinal and entorhinal cortices, and the posterior cortical nucleus of the amygdala. The number of PAP-III mRNA-positive neurons was significantly greater than PAP-I mRNA-positive neurons. The majority of positive neurons co-localized with c-Jun, but not with glutamic acid decarboxylase (GAD). These results may suggest that PAP-I and PAP-III induction in non-GABAergic neurons would protect neurons against damage following seizure.

Localization of CART-Positive Neurons in the Amygdaloid Body and the Relationship between Their Immunoreactivity and the Sex Steroid Level

This is the first study reporting the locations of neurons expressing CART peptide (cocaine-amphetamine-regulated transcript) throughout all the nuclear and paleocortical formations of the amygdaloid body (AB) and demonstrating the effects of sex steroids on immunoreactivity. The immunocytochemical reaction was performed on frontal brain sections from adult rats (seven females in estrus, seven females in metestrus, and seven males). The proportions of immunoreactive neurons to the total number of neurons in adjacent sections stained by the Nissl method were assessed in estrus and metestrus. In the dorsomedial and posterior cortical nuclei and the lateral capsular subnucleus of the central field, the relative numbers of immunoreactive neurons at estrus were significantly greater than at metestrus. These results provide evidence of the involvement of the olfactory and integrative centers of the AB in the pathogenesis of drug dependence and show that new and efficient methods of gene therapy might be developed using the intranasal route for drug administration.

Morphogenesis of the Paleoamygdala During the Early Juvenile Period in Rats

Structural rearrangements in the paleoamygdala during the early juvenile period of development were characterized in studies on 40 Wistar rats of both sexes on days 21, 24, 28, and 31 of postnatal life. Serial frontal sections of the brain stained with cresyl violet by the Nissl method were used to study the cytoarchitectonics of structures within the paleoamygdala (the dorsomedial (Med), the posterior medial (Mep), and posterior cortical (Cop) nuclei) and the dynamics of their formation by recording of planimetric characteristics, with measurements of the numbers of neurons and gliocytes and calculation of glial and apoptotic indexes. The results obtained from these experiments provided evidence for heterochronous morphogenesis and sex-related differences in the differentiation of paleoamygdalar structures. Only the Med was differentiated on day 21 (the beginning of the early juvenile period), while the Mep could be recognized on day 24 and the Cop acquired its characteristic cytoarchitectonics only on day 31 (the beginning of the late juvenile period). Significant gender-related differences in structure were seen in the Med from day 28 and in the Cop and Mep on day 31.

C-Fos expression in the supraoptic nucleus is the most intense during different durations of restraint water-immersion stress in the rat

Restraint water-immersion stress (RWIS) can induce anxiety, hypothermia, and severe vagally-mediated gastric dysfunction. The present work explored the effects of different durations of RWIS on neuronal activities of the forebrain by c-Fos expression in conscious rats exposed to RWIS for 0, 30, 60, 120, or 180 min. The peak of c-Fos induction was distinct for different forebrain regions. The most intense c-Fos induction was always observed in the supraoptic nucleus (SON), and then in the hypothalamic paraventricular nucleus (PVN), posterior cortical amygdaloid nucleus (PCoA), central amygdaloid nucleus (CeA), and medial prefrontal cortex (mPFC). Moreover, body temperature was reduced to the lowest degree after 60 min of RWIS, and the gastric lesions tended to gradually worsen with the prolonging of RWIS duration. These data strongly suggest that these nuclei participate in the organismal response to RWIS to different degrees, and may be involved in the hypothermia and gastric lesions induced by RWIS.

Propagation of the pseudorabies virus particles to the amygdaloid complex after inoculation into rat's insular cortex

Amygdaloid complex (AC) is a heterogeneous group of subcortical nuclei and cortical structures which has a crucial role in the limbic system functions, and which is interconnected with many brain regions. The projections from the AC to the posterior insular cortex, were studied in 5 male adult rats by retrograde marking of neurons with pseudorabies virus (PRV). After inoculation of PRV into the insular cortex, rats were sacrificed after 51, 57 or 72 hours. The serial sections of AC were examined by using immunohistochemistry, with an antibody against PRV. The goal of this study was to identify the nuclei of rat AC with the presence of PRV, to estimate the density of PRV, and also to note the speed of PRV propagation from the posterior insular cortex to AC. Clear distribution of PRV particles in amygdaloid nucleus was observed in the rat brain after 72 hours while in earlier sacrificed animals (51 and 57 hours) there was no positive reaction. The high density of PRV-immunoreactive neurons was in the ipsilateral lateral and basolateral nucleus, as well as in the amygdalohippocampal area. The lower density was in the ipsilateral basomedial, central, medial, posterior cortical nucleus, and nuclei of lateral olfactory tracts, as well as in the contralateral basomedial nucleus. In conclusion, by PRV retrograde tracing was found that the main projections of AC to posterior insular cortex originate from lateral and basolateral nucleus which are known as important regions of sensory convergence of AC, and from the amygdalohyppocampal area, as well.

Histological Atlas and Morphological Features by Nissl Staining in the Amygdaloid Complex of the Horse, Cow and Pig

There are no reports about the amygdaloid complex in horses, cows and pigs. The amygdaloid complex is divided into many subnuclei from the point of histology, and the purpose of this study was to clarify its features by comparison among horses, cows and pigs. Using the Nissl staining method, we examined coronal serial sections of brains from the three species. The division of the amygdaloid subnuclei was performed on the magnified photos and three-dimensional analysis was also performed for the three species. The shape of the amygdala in the horse and cow was an anterior ellipsoid, long and slender in the dorso-ventral direction, posteriorly. In the pig, it was long and slender in the dorso-ventral direction as a whole. The volume of the amygdala in the horse as a percentage of cerebral volume was the biggest among the three species. We divided the amygdala into 27 subnuclei and these subnuclei were classified into 11 subnuclei groups. Features of some subnuclei resembled those of other species, such as rabbit, cat and monkey. Taking into consideration brain development, it was clear that the shapes of the subnuclei were fairly reflected by the brain development within the skull. From the results of three-dimensional analysis, the amygdala was mainly occupied by the lateral and basal nuclei, each occupying about 30% of the amygdala. Features of each species were that the relative size of the posterior cortical nucleus was high in the horse and cow, and the relative size of the amygdalohippocampal area was high in the pig. We concluded that the features of the subnuclei may be related to the functional development.

The magnocellular medial preoptic nucleus I. sources of afferent input

The magnocellular medial preoptic nucleus plays a crucial role in the regulation of male sexual behavior in Syrian hamsters. Histological and behavioral studies suggest that the magnocellular medial preoptic nucleus regulates male mating behavior by integrating chemosensory and hormonal signals. The present study is the first to systematically identify the afferent connections of the magnocellular medial preoptic nucleus by tracing the uptake of cholera toxin B from deposits in the magnocellular medial preoptic nucleus of adult male Syrian hamsters. Our findings indicate that the magnocellular medial preoptic nucleus receives 1) chemosensory input from areas in the main and accessory olfactory pathways including the posterior medial bed nucleus of the stria terminalis, anterior medial, anterior cortical and posterior cortical nuclei of the amygdala; 2) input from steroid responsive structures such as the posterior medial nucleus of the amygdala, bed nucleus of the stria terminalis, lateral septum, anteroventral periventricular nucleus, medial preoptic nucleus, ventromedial nucleus of the hypothalamus and arcuate nucleus; 3) input from structures in the brainstem such as the subparafascicular thalamic nucleus, peripeduncular nucleus and the premamillary nucleus in the hypothalamus that carry sensory information from the genitalia. The major afferent input to the magnocellular medial preoptic nucleus was confirmed by injecting anterograde tracer biotinylated dextran amine into the anterior medical nucleus of the amygdala, the posterodorsal part of the medial nucleus of the amygdala, the posteromedial part of the bed nucleus of the stria terminalis and the posterointermediate part of the bed nucleus of the stria terminalis. Our results support the hypothesis that the magnocellular medial preoptic nucleus is part of the chemosensory pathway that receives chemosensory and hormonal input to regulate mating behavior and suggest that the magnocellular medial preoptic nucleus may utilize information from the genitalia to regulate male mating behavior.

The Paleoamygdala: Cytoarchitectonics, Organization, and the Cytological Characteristics of Its Neurons

The aim of the present work was to compare the cytoarchitectonics, neuronal organization, and cytological characteristics of the dorsomedial, posterior medial, and posterior cortical nuclei of the amygdaloid body (AB) of the rat brain. Series of frontal brain sections stained with cresyl violet and silver nitrate impregnation by the Golgi method were studied. The results showed that rearrangements of the nuclear principle of organization of the gray matter of the nervous system into the screened organization occur within the territory of this complex of nuclei; it consists of a sparsely branched neuron system and contains neuroendocrine cells. It is concluded that this complex of nuclei is unique in terms of its structural organization and the mechanism of development of this part of the AB, which forms in the earliest stages of AB development; it is termed the "paleoamygdala."

Estrogen regulation of cell proliferation and distribution of estrogen receptor‐α in the brains of adult female prairie and meadow voles

Adult female prairie (Microtus ochrogaster) and meadow (M. pennsylvanicus) voles were compared to examine neural cell proliferation and the effects of estrogen manipulation on cell proliferation in the amygdala, ventromedial hypothalamus (VMH), and dentate gyrus of the hippocampus (DG). Unlike prior studies, our study focused on the amygdala and VMH, because they are involved in social behaviors and may underlie behavioral differences between the species. Meadow voles had a higher density of cells labeled with the cell proliferation marker 5-bromo-2'-deoxyuridine (BrdU) in the amygdala and DG than did prairie voles. Treatment with estradiol benzoate (EB) for 3 days increased the density of BrdU-labeled cells in the amygdala, particularly in the posterior cortical (pCorA) and medial (pMeA) nuclei, in meadow, but not prairie, voles. Furthermore, the majority of the BrdU-labeled cells in the pCorA and pMeA displayed either a neuronal or a glial progenitor phenotype, but no species or treatment differences were found in the percentage of neuronal or glial progenitor cells. To understand better estrogen's effects on adult neurogenesis, we also examined estrogen receptor-alpha (ERalpha) distribution. Meadow voles had more ERalpha-labeled cells in the pCorA and VMH, but not in the pMeA or DG, than did prairie voles. In addition, more than one-half of the BrdU-labeled cells in the amygdala of both species coexpressed ERalpha labeling. Together, these data indicate that estrogen alters cell proliferation in a species- and region-specific manner, and some of these effects may lie in the specific localization of estrogen receptors in the adult vole brain.

Dendroarchitectonics of neurons in the posterior cortical nucleus of the amygdaloid body of the rat brain as influenced by gender and neonatal androgenization

The aim of the present work was to identify gender-related differences in the dendroarchitectonics of neurons in the posterior cortical nucleus of the amygdaloid body and the role of androgens in forming the dendroarchitectonics during the period of sexual differentiation of the rat brain. Golgi staining showed that long-axon, sparsely branched neurons in males had large numbers of primary dendrites, while long-axon densely branched neurons had a greater total dendrite length in females. Administration of testosterone propionate (1250 microg) to females on postnatal day 5 increased the number of primary dendrites in long-axon, sparsely branched neurons in adults as compared with the number in control females; treatment also produced a significant increase in dendrite length in long-axon, densely branched neurons, leading to an increase in the area of the dendritic field.

The distribution of serotonergic fibers in the macaque monkey amygdala: An immunohistochemical study using antisera to 5-hydroxytryptamine

Though both the amygdala and the serotonin system appear to play critical roles in regulating fear and anxiety, little is known regarding the organization of serotonergic inputs to the primate amygdala. The present study employed immunohistochemistry to determine the distribution of serotonin fibers in the macaque amygdala. The brains of three adult male Macaca fascicularis monkeys were prepared for histological analysis using a polyclonal antibody to serotonin. The macaque amygdala is densely innervated by serotonergic fibers and demonstrates a distinctive pattern of fiber distribution and density among the 13 nuclei and cortical areas. The highest density of 5-hydroxytryptamine immunoreactive fibers is observed in the central nucleus, the nucleus of the lateral olfactory tract, the paralaminar nucleus, the anterior amygdaloid area and a small region of the amygdalohippocampal area. Moderate fiber densities are found in portions of the basal, lateral, and intercalated nuclei. The lowest fiber densities are observed in the accessory basal, posterior cortical, anterior cortical and medial nuclei, and in subregions of the periamygdaloid cortex. The present study provides evidence that the serotonergic system can have substantial influence on the ongoing activity of the amygdaloid complex.

The effects of sex and neonatal androgenization on neuron dendroarchitectonics in amygdala posterior cortical nucleus

Sex differences in neuron dendroarchitectonics of the amygdala posterior cortical nucleus of adult rats were described for the first time using the Golgi method. Long-axon sparse-branched neurons in male rats possessed a larger number of primary dendrites, while female rats had long-axon dense-branched neurons with longer dendrites. Injection of testosterone propionate at 1250 µg to females on day 5 after birth resulted in a greater number of primary dendrites of long-axon sparse branched neurons in adults, as compared to that in the control. Dendrites of long-axon sparse-branched neurons became much longer, thus enlarging the dendrite area.