Differential evolution of PSA-NCAM expression during aging of the rat telencephalon

Changes in the ability of neuronal networks to undergo structural remodeling may be involved in the age-associated cognitive decline. The polysialylated form of the neural cell adhesion molecule (PSA-NCAM) declines dramatically during postnatal development, but persists in several regions of the young-adult rat telencephalon, where it participates, through its anti-adhesive properties, in neuronal structural plasticity. However, PSA-NCAM expression during aging has only been studied in the dentate gyrus and the piriform cortex layer II, where it is strongly downregulated in adult (middle-aged) individuals. Using immunohistochemistry, we have observed that in most of the telencephalic areas studied the number of PSA-NCAM expressing cells and the intensity of PSA-NCAM expression in the neuropil remains stable during aging. Old rats only show decreases in the number of PSA-NCAM expressing cells in the lateral amygdala and retrosplenial cortex, and in neuropil expression of stratum lucidum. Given the role of PSA-NCAM in neuronal plasticity, the present results indicate that, even during aging, many regions of the CNS may display neurite, spine or synaptic remodeling.     

A gradient of plasticity in the amygdala revealed by cortical and subcortical stimulation, in vivo

Projections to the amygdala from various cortical and subcortical areas terminate in different nuclei. In the present study we examined long-term potentiation of synaptic transmission in the lateral or the basal amygdaloid nuclei by theta burst stimulation of thalamic vs. cortical sensory projections in the anesthetized rat. Although both the medial geniculate nucleus and the dorsal perirhinal cortex have direct projections to lateral nucleus, only the thalamic stimulation induced long-term potentiation of field potentials recorded in the lateral nucleus. In contrast, cortical (ventral perirhinal cortex) but not thalamic stimulation induced long-term potentiation in the basal nucleus.Since the thalamic pathway is believed to process simple/unimodal stimulus features, and the perirhinal cortex complex/polymodal sensory representations, the dissociation of long-term potentiation in lateral and basal nuclei suggests that the basal nucleus may serve as an amygdaloid sensory interface for complex stimulus information similar to the role of the lateral nucleus in relation to relatively simple representations. Thus plasticity of simple and complex representations may involve different amygdala inputs and circuits.     

Topographic organization of projections from the amygdala to the hypothalamus of the rat

Afferent fibers from the amygdala to subdivisions of lateral, ventromedial and dorsomedial hypothalamic nuclei were investigated in rat by retrograde transport of horseradish peroxidase. Small (intranuclear size) peroxidase deposits were placed in hypothalamic nuclei by iontophoresis of a tracer solution containing poly-L-alpha-ornithine which greatly limited diffusion. The medial, central and amygdalo-hippocampal nuclei of the amygdala were found to be the major donors of amygdaloid afferent fibers to the hypothalamus, but there was also substantial labeling of somata in cortical, basomedial, basolateral and lateral amygdaloid nuclei and the intra-amygdaloid bed nucleus of the stria terminalis. No fibers projected from the posterior cortical nucleus of the amygdala to the hypothalamus. Most amygdaloid projections to the lateral hypothalamic area originated in the anterior half of the amygdala, while projections to the ventromedial hypothalamic nucleus arose along the entire length of the amygdala except the posterior cortical nucleus. The amygdalo-hippocampal area projects to the medial hypothalamus. Other amygdaloid nuclei project to both the medial and lateral hypothalamic nuclei. These topographic organizations of amygdaloid afferent fibers to various subdivisions of the hypothalamic nuclei are discussed and compared with other anatomical studies on these connections.     

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.     

Subcortical projections to the prefrontal cortex in the rat as revealed by the horseradish peroxidase technique

The sources and distribution of subcortical afferents to the anterior neocortex were investigated in the rat using the horseradish peroxidase technique. Injections into the prefrontal cortex labelled, in addition to the mediodorsal thalamic nucleus, neurons in a total of fifteen subcortical nuclei, distributed in the basal telencephalon, claustrum, amygdala, thalamus, subthalamus, hypothalamus, mesencephalon and pons. Of these, the projections from the zona incerta, the lateroposterior thalamic nucleus, and the parabrachial region of the caudal mesencephalon to the prefrontal cortex have not previously been described.Different parts of the mediodorsal thalamic nucleus project to different areas of the frontal cortex. Thus, horseradish peroxidase injections in the most ventral pregenual part of the medial cortex labelled predominantly neurons in the medial anterior and dorsomedial posterior parts of the mediodorsal nucleus; injections into the more dorsal pregenual area labelled only neurons in the lateral and ventral parts of the nucleus; injections placed supragenually labelled neurons in the dorsolateral posterior part of the nucleus; and injections into the dorsal bank of the anterior rhinal sulcus labelled neurons in the centromedial part of the nucleus.Several other subcortical nuclei had projections overlapping with that of the mediodorsal thalamic nucleus. Five different types of such overlap were distinguished: (1) cell groups labelled after horseradish peroxidase injections into one of the subfields of the projection area of the mediodorsal nucleus (defined as the prefrontal cortex), but not outside this area (parataenial nucleus of the thalamus); (2) cell groups labelled both after injection into a subfield of the projection area of the mediodorsal nucleus and after injections in a restricted area outside this area (anteromedial, ventral and laterposterior thalamic nuclei); (3) cell groups labelled after injections into all subfields of the mediodorsal nucleus projection area, but not outside this area (ventral tegmental area, basolateral nucleus of amygdala); (4) cell groups labelled after injections into any area of the anterior neocortex, including the mediodorsal nucleus projection area (parabrachial neurons of the posterior mesencephalon); (5) cell groups labelled after all neocortical injections investigated (claustrum, magnocellular nuclei of the basal forebrain, lateral hypothalamus, zona incerta, intralaminar thalamic nuclei, nuclei raphe dorsalis and centralis superior, and locus coeruleus).We can draw the following conclusions from these and related findings. First, because of the apparent overlap of projections of the mediodorsal, the anteromedial and ventral thalamic nuclei in the rat, parts of the prefrontal cortex can also be called ‘cingulate’ and ‘premotor’. Second, on the basis of projections from parts of the mediodorsal nucleus, the prefrontal cortex of the rat can be subdivided into areas corresponding to those in other species. Third, the neocortex receives afferents from a large number of subcortical cell groups outside the thalamus, distributed from the telencephalon to the pons; however, the prefrontal cortex seems to be the only neocortical area innervated by the ventral tegmental area and amygdala. Finally, neither the prefrontal cortex nor the mediodorsal thalamic nucleus receives afferents from regions directly involved in sensory and motor functions.     

Chronic restraint stress down-regulates amygdaloid expression of polysialylated neural cell adhesion molecule

The amygdala is a brain area which plays a decisive role in fear and anxiety. Since exposure to chronic stress can induce profound effects in emotion and cognition, plasticity in specific amygdaloid nuclei in response to prior stress has been hypothesized to account for stress-induced emotional alterations. In order to identify amygdala nuclei which may be affected under chronic stress conditions we evaluated the effects of 21-days chronic restraint stress on the expression of a molecule implicated crucially in alterations in structural plasticity: the polysialylated neural cell adhesion molecule. We found that polysialylated neural cell adhesion molecule-immunoreactivity within the amygdala, present in somata and neuronal processes, has a regional gradient with the central medial and medial amygdaloid nuclei showing the highest levels. Our results demonstrate that chronic restraint stress induced an overall reduction in polysialylated neural cell adhesion molecule-immunoreactivity in the amygdaloid complex, mainly due to a significant decrease in the central medial amygdaloid and medial amygdaloid nuclei. Our data suggest that polysialylated neural cell adhesion molecule in these nuclei may play a prominent role in functional and structural remodeling induced by stress, being a potential mechanism for cognitive and emotional modulation. Furthermore, these finding provide the first clear evidence that life experiences can regulate the expression of polysialylated neural cell adhesion molecule in the amygdaloid complex.     

磷酸化的蛋白激酶p44／42MAPK在成年大鼠脑内的分布

目的：研究活化形式的p44／42MAPK在成年正常大鼠脑内的分布。方法：免疫组织化学方法（ABC法）。结果：磷酸化的p44／42MAPK在正常大鼠脑内有广泛的表达,出现在许多核团,特别在岛皮质、感觉运动及视、听皮质、扣带前皮质、海马尾侧的内嗅区、内侧杏仁核、皮质杏仁核和中介核、视上核、蓝斑、臂旁外侧核、小脑Purkinje细胞、A5区、旁巨细胞外侧核、吻侧（C1区）和尾侧（A1区）延髓腹外侧网状结构等,阳性结构主要见于神经元的胞浆、胞核和突起内,在部分脑膜细胞和少突胶质细胞内也有表达,结论：活化的p44／42MAPK在脑内的广泛存在提示其作为重要的信号转导分子在正常状的脑功能活性中可能起重要作用。     

Selective learning and memory impairments in mice deficient for polysialylated NCAM in adulthood

The neural cell adhesion molecule (NCAM) has been implicated in regulating synaptic plasticity mechanisms as well as memory consolidation processes. Attachment of polysialic acid to NCAM (PSA-NCAM) has been reported to down-regulate its adhesive forces, a process hypothesized to be implicated in synapse selection after learning experiences. PSA-NCAM has been critically implicated in hippocampus-related synaptic plasticity and memory storage, but information about its functional role in other brain areas remains scarce. Here, we studied mice deficient for polysialyltransferase-1 (ST8SialV/PST-1), an enzyme which attaches PSA to NCAM during postnatal development and adulthood, and whose deficiency results in a drastic reduction of PSA-NCAM expression throughout the brain in adulthood. Mice were tested for their performance in the water maze and auditory fear conditioning (AFC). We report that ST8SiaIV knockout mice were impaired in spatial as well as reversal learning in the water maze. On the other hand, AFC was intact and ST8SiaIV mice exhibited no impairments in the acquisition or retention of cued fear memories. Spatial orientation learning and reversal learning require complex integration of spatial information and response selection involving the hippocampus and prefrontal cortex, whereas cued fear conditioning is an associative type of emotional memory that highly depends on amygdala function. Therefore, our results indicate that PSA-NCAM contributes differentially to learning processes that differ in the nature of the neural computations involved, which probably reflects a differential role of this molecule in different brain regions.     

The cingulate bridge between allocortex, isocortex and thalamus.

The Fink-Heimer silver impregnation and the autoradiographic methods were used to study the fiber projections of the cingulate cortex in the squirrel monkey. It was found that this cortex provides inputs to the straitum, thalamus and several areas of isocortex. Evidence was found for a number of fiber projections (1) Fibers from the anterior limbic area were traced to the central part of the head of the caudate nucleus, putamen, septum, dorsomedial nucleus of the thalamus, anterior hypothalamus and lateral basal nucleus of the amygdala. (2) Projections from the cingulate area were traced to the lateral part of the head of the caudate nucleus, putamen, and to the centromedian, anterior, lateral dorsal, and lateral ventral thalamic nuclei and to medial nuclei of the base of the pons. (3) There were porjections from the retrosplenial area of the anterior, lateral dorsal, dorsomedial, and posterior thalamic nuclei and lateral nuclei of the pons. These results indicate that most of the cingulate gyrus is an intermediate structure between the thalamus and overlying cortex. The anterior limbic area forms a bridge between the thalamus and other areas of the cingulate gyrus and the frontal cortex. (4) the retrosplenial area and the posterior part of the cingulate area bridge the adjacent visual snesory association cortex and pelvic areas of the snesory motor cortex, respectively. These areas of the cingulate gyrus project directly to the striatum as well as to the thalamus, structurally providing limbic system input to subcortical motor structures.     

The cingulate bridge between allocortex,isocortex and thalamus

The Fink-Heimer silver impregnation and the autoradiographic methods were used to study the fiber projections of the cingulate cortex in the squirrel monkey. It was found that this cortex provides inputs to the striatum, thalamus and several areas of isocortex. Evidence was found for a number of fiber projections (1) Fibers from the anterior limbic area were traced to the central part of the head of the caudate nucleus, putamen, septum, dorsomedial nucleus of the thalamus, anterior hypothalamus and lateral basal nucleus of the amygdala. (2) Projections from the cingulate area were traced to the lateral part of the head of the caudate nucleus, putamen, and to the centromedian, anterior, lateral dorsal, and lateral ventral thalamic nuclei and to medial nuclei of the base of the pons. (3) There were projections from the retrosplenial area of the anterior, lateral dorsal, dorsomedial, and posterior thalamic nuclei and lateral nuclei of the pons. These results indicate that most of the cingulate gyrus is an intermediate structure between the thalamus and overlying cortex. The anterior limbic area forms a bridge between the thalamus and other areas of the cingulate gyrus and the frontal cortex. (4) The retrosplenial area and the posterior part of the cingulate area bridge the adjacent visual sensory association cortex and pelvic areas of the sensory motor cortex, respectively. These areas of the cingulate gyrus project directly to the striatum as well as to the thalamus, structurally providing limbic system input to subcortical motor structures.     

Simultaneous induction of long-term potentiation in the hippocampus and the amygdala by entorhinal cortex activation: mechanistic and temporal profiles

The medial temporal lobe, including the entorhinal cortex, the amygdala and the hippocampus, has an important role in learning and memory, and its circuits exhibit synaptic plasticity (long-term potentiation [LTP]). The entorhinal cortex is positioned to exert a potent influence on the amygdala and the hippocampus given its extensive monosynaptic projections to both areas. We therefore studied the effects of activation of the entorhinal cortex with simultaneous recording of LTP in the hippocampus and amygdala in the anesthetized rat. theta Burst stimulation of the lateral entorhinal cortex induced LTP simultaneously in the basal amygdaloid nucleus and in the dentate gyrus. However, the mechanisms involved in the induction of LTP in the two areas differed. The N-methyl-D-aspartate receptor antagonist 3-[(+/-)-2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid delivered 1 h before LTP induction (10 mg/kg, i.p.), blocked LTP in the dentate gyrus but not in the amygdala. In addition we found that the basal amygdala as well as the dentate gyrus sustained late-phase LTP (10 h) which may participate in memory encoding and/or modulation processes. Overall, the results suggest a coordinating role for the entorhinal cortex by simultaneously modulating activity and plasticity in these structures, albeit through different mechanisms. Interactive encoding of this sort is believed to endow memories with a different, more integrative, quality than when either pathway is activated alone.     

A description of the amygdalo-hippocampal interconnections in the macaque monkey

The interconnections between the amygdala and the hippocampal formation were investigated in the macaque monkey using anterograde tracers. The hippocampal inputs to the amygdala arose from the subicular and entorhinal cortices and passed through the angular bundle to terminate principally in the medial basal and lateral basal nuclei, with lighter termination in the lateral nucleus, the periamygdaloid cortex, and the cortical-transition area. The majority of these amygdaloid inputs arose from the rostral hippocampal formation although there was equivocal evidence of an additional projection from the caudal hippocampus to the central nucleus. Projections arose from many of the amygdaloid nuclei to terminate in the molecular layer of the amygdalo-hippocampal area and the adjacent stratum moleculare of the uncal portion of the hippocampus. The accessory basal, lateral basal, and medial basal nuclei also projected to the most rostral portions of the stratum moleculare of fields CA1-3, the heaviest termination occurring in field CA3. Additional projections from the basal nuclei terminated in the prosubiculum, presubiculum, and parasubiculum. The heaviest entorhinal inputs arose from the accessory basal and lateral nuclei and terminated in layers I, II, and III of areas 28b, 28i, and the prorhinal cortex. The major amygdaloid input to the perirhinal cortex arose from the lateral basal nucleus.     

Ultrastructure and synaptic associations of auditory thalamo-amygdala projections in the rat

Summary Projections from the acoustic thalamus to the lateral nucleus of the amygdala (AL) have been implicated in the formation of emotional memories. In order to begin elucidating the cellular basis of emotional learning in this pathway, the ultrastructure and synaptic associations of acoustic thalamus efferents terminating in AL were studied using wheat-germ agglutinated horse-radish peroxidase (WGA-HRP) and Phaseolus vulgaris Leucoagglutinin (Pha-L) as ultrastructural anterograde axonal markers. The tracers were injected into those areas of the thalamus (medial division of the medial geniculate body and posterior intralaminar nucleus, MGM/PIN) known both to project to AL and to receive afferents from the inferior colliculus. Terminals labeled with WGA-HRP or Pha-L in AL contained mitochrondria and many small, round clear vesicles and 0–3 large, dense-core vesicles. Most labeled terminals formed asymmetric synapses on unlabeled dendrites; of these the majority were on dendritic spines. These data demonstrate that projections from the acoustic thalamus form synapses in AL and provide the first characterization of the ultrastructure and synaptic associations of sensory afferent projections to the amygdala.Abbreviations ABL basolateral nucleus of the amygdala - ABM basomedial nucleus of the amygdala - ABV ventral basolateral nucleus of the amygdala - ACE central nucleus of the amygdala - ACO cortical nucleus of the amygdala - AM medial nucleus of the amygdala - APT anterior pretectal area - AST amygdalo-striatal transition area - AL lateral nucleus of the amygdala - CI internal capsule - CG central gray - CP cerebral peduncle - CPU caudateputamen - EN endopiriform area - GP globus pallidus - I intercalated nucleus of the amygdala - OT optic tract - PIN posterior intralaminar nucleus - PIR piriform cortex - POM medial posterior thalamic complex - PP peripeduncular area - PR perirhinal cortex - SC superior colliculus - SG suprageniculate nucleus - RN red nucleus     

Differential patterns of extracellular signal-regulated kinase-1 and -2 phosphorylation in rat limbic brain regions after short-term and long-term inhibitory avoidance learning

Activation of the extracellular signal-regulated kinase-1 and -2 has been shown to be required for neural plasticity and memory. Previous pharmacological studies have demonstrated that inhibition of extracellular signal-regulated kinase-1 and -2 blocks inhibitory avoidance retention. The aim of the present study was to investigate the different neural substrates underlying short- and long-term inhibitory avoidance learning and memory in rats using phosphorylated extracellular signal-regulated kinase-1 and -2 labeling as an index of plasticity. Short- and long-term retention tests were given 10 min or 24 h after inhibitory avoidance training. A significant elevation in the number of phosphorylated extracellular signal-regulated kinase-1 and -2-immunoreactive neurons was observed in area 1 of anterior cingulate cortex, the secondary motor cortex, lateral orbital cortex, claustrum, and the medial amygdala nucleus after the short-term inhibitory avoidance test. After the long-term retention test, phosphorylated extracellular signal-regulated kinase-1 and -2-immunoreactive neurons were localized in area 1 of anterior cingulate cortex, prelimbic cortex, and the central nucleus of amygdala. This suggests that phosphorylated extracellular signal-regulated kinase-1 and -2-immunoreactivity may reveal different brain regions involved in the storage of short- and long-term aversive memories.     

Afferent connections of the interstitial nucleus of the posterior limb of the anterior commissure and adjacent amygdalostriatal transition area in the rat

The interstitial nucleus of the posterior limb of the anterior commissure is, like the striatum, very rich in tyrosine hydroxylase and acetylcholinesterase, but on the basis of most other neurochemical criteria displays features that are typical of the extended amygdala (Alheid, de Olmos and Beltramino, 1995). Its afferent connections were examined in the rat with retrograde (cholera toxin B subunit) and anterograde (Phaseolus vulgaris leucoagglutinin) tracers and compared to those of the neighboring amygdalostriatal transition area and central amygdaloid nucleus. Deposits of cholera toxin B subunit in the interstitial nucleus of the posterior limb of the anterior commissure result in retrograde labeling that is similar to that seen after cholera toxin B subunit injections in the central amygdaloid nucleus. Retrogradely labeled cells are found in insular, infralimbic, prelimbic, piriform, amygdalopiriform transition, entorhinal and perirhinal cortices, as well as in temporal field CA1 of Ammon horn and ventral subiculum, amygdala (nucleus of the lateral olfactory tract, anterior amygdaloid area, anterior cortical, posterolateral cortical, anterior and posterior basomedial, intercalated cells, basolateral and lateral nuclei), and extended amygdala, primarily in its central division. The latter includes the lateral bed nucleus of the stria terminalis, dorsal portions of the sublenticular region, the lateral pocket of the supracapsular bed nucleus of the stria terminalis and the central amygdaloid nucleus. Retrogradely labeled cells are also seen in midline thalamic nuclei, lateral hypothalamus, ventral tegmental area, retrorubral field, dorsal raphe nucleus, pedunculopontine and dorsolateral tegmental nuclei, locus coeruleus and parabrachial area. The central extended amygdala, lateral hypothalamus and parabrachial area display a substantial retrograde labeling only when the injection involves districts of the interstitial nucleus of the posterior limb of the anterior commissure apposed to the pallidum, i.e. its medial part. Our anterograde results confirm that projections from the lateral bed nucleus of the stria terminalis and central amygdaloid nucleus to the interstitial nucleus of the posterior limb of the anterior commissure target its medial part. They also indicate that structures which provide major afferents to the central extended amygdala (the lateral and posterior basolateral amygdaloid nuclei and the amygdalopiriform transition area) innervate chiefly the medial part of the interstitial nucleus of the posterior limb of the anterior commissure and, to a much lesser degree, its lateral part. The piriform cortex, which has well-acknowledged projections to the ventral striatum, innervates only the rostral sector of the interstitial nucleus of the posterior limb of the anterior commissure. Taken together, these data indicate that the medial part of the interstitial nucleus of the posterior limb of the anterior commissure is closely related to the central extended amygdala. Rostral and lateral parts of the interstitial nucleus of the posterior limb of the anterior commissure, on the other hand, appear as transitional territories between the central extended amygdala and ventral striatum. The afferent connections of the zone traditionally termed amygdalostriatal transition area are in general similar to those of the caudate-putamen, which does not receive projections from the central extended amygdala. After cholera toxin B subunit injections in the caudoventral globus pallidus, a dense retrograde labeling is observed in the amygdalostriatal transition area and overlying striatum, but not in the interstitial nucleus of the posterior limb of the anterior commissure. Our results suggest that the interstitial nucleus of the posterior limb of the anterior commissure and the amygdalostriatal transition area are engaged in distinct forebrain circuits; the former is a dopamine-rich territory intimately related to the central ext     

Alterations in the expression of PSA-NCAM and synaptic proteins in the dorsolateral prefrontal cortex of psychiatric disorder patients

Alterations in the structure and physiology of the prefrontal cortex (PFC) have been found in different psychiatric disorders and some of them involve inhibitory networks, especially in schizophrenia and major depression. Changes in the structure of these networks may be mediated by the polysialylated neural cell adhesion molecule (PSA-NCAM), a molecule related to neuronal structural plasticity, expressed in the PFC exclusively by interneurons. Different studies have found that PSA-NCAM expression in the hippocampus and the amygdala is altered in schizophrenia, major depression and animal models of these disorders, in parallel to changes in the expression of molecules related to inhibitory neurotransmission and synaptic plasticity. We have analyzed post-mortem sections of the dorsolateral PFC from the Stanley Neuropathology Consortium, which includes controls, schizophrenia, bipolar and major depression patients, to check whether similar alterations occur. PSA-NCAM was found in neuronal somata and neuropil puncta, many of which corresponded to interneurons. PSA-NCAM expression was only reduced significantly in schizophrenic patients, in parallel to a decrease in glutamic acid-decarboxylase-67 (GAD67) and to an increased expression of vesicular glutamate transporter 1 (VGLUT1) in the white matter. Depressed patients showed significant decreases in synaptophysin (SYN) and VGLUT1 expression. Whereas in bipolar patients, decreases in VGLUT1 expression have also been found, together with a reduction of GAD67. These results indicate that the expression of synaptic proteins is altered in the PFC of patients suffering from these disorders and that, particularly in schizophrenia, abnormal PSA-NCAM and GAD67 expression may underlie the alterations observed in inhibitory neurotransmission.     

Interamygdaloid connections in the rat studied by the horseradish peroxidase method

Neurons of the rat amygdaloid body were labeled with horseradish peroxidase following its injection into contralateral nuclei of the amygdala. The results strongly suggest that there is a contralateral amygdaloid projection from the basal (dorsal and ventral) nuclei of amygdala; it terminates in the medial, central and lateral nucleus. True commissural connections were found only between posterior parts of the cortical nuclei of amygdala and between homonymous areas of the piriform cortex.     

Amygdala projections to central amygdaloid nucleus subdivisions and transition zones in the primate

In rats and primates, the central nucleus of the amygdala (CeN) is most known for its role in responses to fear stimuli. Recent evidence also shows that the CeN is required for directing attention and behaviors when the salience of competing stimuli is in flux. To examine how information flows through this key output region of the primate amygdala, we first placed small injections of retrograde tracers into the subdivisions of the central nucleus in Old world primates, and examined inputs from specific amygdaloid nuclei. The amygdalostriatal area and interstitial nucleus of the posterior limb of the anterior commissure (IPAC) were distinguished from the CeN using histochemical markers, and projections to these regions were also described. As expected, the basal nucleus and accessory basal nucleus are the main afferent connections of the central nucleus and transition zones. The medial subdivision of the central nucleus (CeM) receives a significantly stronger input from all regions compared to the lateral core subdivision (CeLcn). The corticoamygdaloid transition zone (a zone of confluence of the medial parvicellular basal nucleus, paralaminar nucleus, and the sulcal periamygdaloid cortex) provides the main input to the CeLcn. The IPAC and amygdalostriatal area can be divided in medial and lateral subregions, and receive input from the basal and accessory basal nucleus, with differential inputs according to subdivision. The piriform cortex and lateral nucleus, two important sensory interfaces, send projections to the transition zones. In sum, the CeM receives broad inputs from the entire amygdala, whereas the CeLcn receives more restricted inputs from the relatively undifferentiated corticoamygdaloid transition region. Like the CeN, the transition zones receive most of their input from the basal nucleus and accessory basal nucleus, however, inputs from the piriform cortex and lateral nucleus, and a lack of input from the parvicellular accessory basal nucleus, are distinguishing afferent features.     

Amygdalar connections with middle and inferior temporal gyri of the monkey

The origins and terminations of the amygdalar connections with middle (ITm) and inferior temporal (ITi) gyri of inferotemporal cortex (area TE) were studied in Japanese monkeys by the horseradish peroxidase method. The ITm gyrus received a major projection from the lateral basal nucleus and a minor one from the accessory basal nucleus of the amygdala, whereas it sent a major projection to the lateral nucleus and a minor one to the lateral basal nucleus. The ITi gyrus had only minor amygdalar projections from the medial basal nucleus and to the medial basal and lateral nuclei.