Distribution of neuropeptides in the limbic system of the rat: the amygdaloid complex

Central somatostatin systems revealed with monoclonal antibodies

The distribution of central neurons displaying somatostatin immunoreactivity was studied using three monoclonal antibodies to cyclic somatostatin. The sensitive ABC immunoperoxidase technique was employed. A large number of positive cell groups including many previously undescribed populations were detected throughout the brain and spinal cord. Telencephalic somatostatin neurons included periglomerular cells in the olfactory bulb, mitral cells in the accessory olfactory bulb, and multipolar cells in the anterior olfactory nuclei, neocortex, amygdala, hippocampus, lateral septum, striatum, and nucleus accumbens. Within the hypothalamus, positive neurons were found in the periventricular, suprachiasmatic, and arcuate nuclei, and throughout the anterior and lateral hypothalamus. The entopeduncular nucleus and zona incerta contained many positive neurons, and the lateral habenula had a dense terminal field suggesting a pallidohabenula somatostatin pathway. Somatostatin neurons were also found in association with many sensory systems. Positive cells were present in the superior and inferior colliculi, the ventral cochlear nuclei, the ventral nucleus of the lateral lemniscus, nucleus cuneatus, nucleus gracilus, and the substantia gelatinosa. Various cerebellar circuits also displayed somatostatin immunoreactivity. Golgi cells throughout the cerebellar cortex were intensely stained, and some Purkinje cells in the paraflocculus also showed a positive reaction. Positive fibers were present in the granular layer and large varicose fibers were present in the inferior cerebellar peduncle. Many nuclei known to project to the cerebellum, including the nucleus reticularis tegmenti pontis, the medial accessory inferior olive, the nucleus prepositus hypoglossi, and many areas of the reticular formation contained positive neurons. These studies demonstrate that these new monoclonal antibodies are of great value for the study of central somatostatin systems. Previously described somatostatin systems are readily detected with these antibodies, and in addition, many otherwise unrecognized somatostatin cell groups have been discovered.

Morphology of peptide-containing neurons in the rat basolateral amygdaloid nucleus

The peroxidase-antiperoxidase (PAP) immunohistochemical technique was used to identify neurons in the basolateral amygdaloid nucleus (BL) that contain vasoactive intestinal polypeptide (VIP), somatostatin (SOM) or cholecystokinin (CCK). Examination of immunostained neurons demonstrated that most, if not all, of these peptide-containing cells correspond to spine-sparse class II neurons recognized in Golgi studies. Each type of peptide-containing perikaryon in BL exhibits a distinct size distribution which, in part, accounts for the broad size range of class II neurons noted in Golgi studies.

Autoradiographic localization of a non-reducible somatostatin analog (125I-CGP 23996) binding sites in the rat brain: comparison with membrane binding

The regional distribution of somatostatin binding sites in the rat brain was determined by quantitative autoradiography, using 125I-CGP 23996, a non-reducible somatostatin analog. In preliminary experiments, kinetic properties of 125I-CGP 23996 binding to rat brain membranes and slide mounted frozen brain sections were compared and found similar. In addition, distribution of 125I-CGP 23996 and 125I-N-Tyr-SRIF14 binding sites on membrane prepared from 10 different rat brain structures were closely correlated (r = 0.91, 2 p less than 0.01), indicating that the non-reducible analog recognizes the same binding site as the Tyr-extended native peptide. Highest levels of 125I-CGP 23996 binding sites were found in anterior temporal, frontal and cingular cortex as well as hippocampus. Moderate levels were found in the remaining part of the limbic system including amygdala, olfactory tubercles and bed nucleus of the stria terminalis. In the brain stem, nuclei involved in the auditory system such as the ventral cochlear nucleus and the superior olive nucleus, contained high levels of 125I-CGP 23996 binding sites. The distribution of 125I-CGP 23996 binding sites roughly correlated with that of the endogenous peptide in most structures, except in the mediobasal hypothalamus.

Studies on cholecystokinin-containing neuronal pathways in rat cerebral cortex and striatum

Lesion experiments were performed to investigate the origin of CCK-containing afferents of the striatum. All the subdivisions of the striatum that were investigated seem to receive CCK afferents from dorsolateral and lateral neocortical areas. However, destruction of these cortical areas alone did not reduce CCK-IRC in the striatum. Only after an additional parasagittal severance of the corpus callosum were significant decreases in CCK-IRC of all striatal subdivisions observed. Thus, CCK neurons in ipsilateral midline areas (such as the cingulate cortex) or, more likely, in contralateral cortical areas, seem to project to the striatum of one side. The CCK fibers seem to enter the striatum via the capsula externa, since a lesion of this structure has been shown to diminish the CCK-IRC in the striatum. In addition, the dorsomedial part of the head of the striatum may receive a projection of CCK fibers from the anterior cingulate area. A series of lesions which severed the afferents of structures caudal to the striatum, that is, the amygdaloid complex and the ventral tegmental area plus substantia nigra, did not reduce CCK-IRC in the striatum. Some of these lesions even significantly enhanced CCK-IRC in several subdivisions of the ipsilateral and contralateral striatum. Further studies will be necessary to cast some light on these caudal CCK afferents to the striatum, which are obviously extremely complex.

Immunohistochemical analysis of the early ontogeny of the neuropeptide Y system in rat brain

The distribution of neuropeptide Y in the developing rat brain was studied with immunocytochemistry, using the peroxidase-antiperoxidase method. Immunoreactive perikarya were first seen on embryonic day 13 and staining of fibres appeared from embryonic day 15 onwards: perikaryal staining was generally more intense prenatally than after birth. Areas rich in neuropeptide Y immunostaining included the monoaminergic regions of the brain stem from embryonic day 13 (especially the lateral reticular nucleus and the medullary reticular formation), the dorsal mesencephalon (with spots of immunoreactivity in the outer subventricular zone at embryonic days 13 or 14 and many cells and fibres in the inferior colliculus from embryonic days 16-20) and the olfactory tubercle/ventral striatum from embryonic day 15 until birth. The period of development of cortical neurones extended from embryonic day 19 until postnatal day 21. A hitherto unreported feature unique to neuropeptide Y was the presence in certain parts of the cerebral cortex of transient cells at the base of the cortical plate bearing radial processes which transverse its width. They were present from embryonic day 17 until postnatal day 4 and were maximally developed at embryonic days 20 or 21, contributing at this age a substantial fibre projection through the immature corpus callosum. The abundance of neuropeptide Y in the prenatal rat brain suggests it may play an important role in development.

The comparative distribution of enkephalin, dynorphin and substance P in the human globus pallidus and basal forebrain

Three neuropeptides, enkephalin, dynorphin, and substance P appear in the globus pallidus in a unique pattern termed woolly fibers as described previously [Haber and Nauta (1983) Neuroscience 9, 245-260]. The comparative distribution of these fibers are described in the human globus pallidus and basal forebrain area. The results show two main points: The human globus pallidus is a larger, more intricately shaped structure than previously thought, invading several limbic-related basal forebrain regions. There are differences in the distribution patterns of the neuropeptides described, so that they are found in overlapping, but not matching regions. The relationship between the peptide distribution and what is known about the functional (limbic vs motor) circuitry of the region is discussed.

Huntington's disease is accompanied by changes in the distribution of somatostatin-containing neuronal processes

The distribution of somatostatin-like immunoreactivity in the caudate, putamen, globus pallidus and ventral mesencephalon of the normal human brain has been studied with immunocytochemical techniques, and compared to that seen in Huntington's disease. Within the normal striatum, sparsely distributed varicose fibers and a population of medium-sized neurons were stained. In Huntington's disease, somatostatin immunoreactive striatal neurons appear to degenerate in proportion to the loss of striatal tissue, but there is an increase in the density of immunostained varicose fibers. In contrast, the pattern and amount of fiber staining in the substantia nigra appeared virtually unchanged from that seen in the normal brain. The morphology of striatal perikarya containing somatostatin-like immunoreactivity and the patterns of fiber staining in normal and Huntington's disease pallidum and substantia nigra suggest that striatal neurons containing somatostatin-like immunoreactivity are local circuit neurons.

Location of neuronal tangles in somatostatin neurones in Alzheimer's disease

Senile dementia of the Alzheimer type is a chronic, progressive neuropsychiatric condition characterized clinically by global intellectual impairment and neuropathologically by the presence of numerous argyrophilic plaques and tangles. Neurochemical investigations have established loss of the cholinergic and aminergic projections to the cerebral cortex and a loss of the content of somatostatin, with preservation of cholecystokinin and vasoactive intestinal polypeptide, neuropeptides also located in cells intrinsic to the cortex. We describe here the relationship between cortical somatostatin immunoreactivity and the plaques and tangles of diseased tissue by immunocytochemical and silver impregnation techniques on paraffin-embedded tissue. In sections of Alzheimer's tissue, cortical somatostatin-immunoreactive perikarya exhibited morphological changes consistent with neuronal degeneration. Silver-stained material immunostained subsequently showed that many neurones containing tangles were also somatostatin positive. No such colocalization was observed using antisera to other neuropeptides. Our findings indicate that a subclass of somatostatin-positive neurones are affected selectively in Alzheimer's disease and that these neurones also contain neuronal tangles. Thus, destruction of somatostatin-containing neurones is an early and perhaps critical event in the disease process.

Comparison of substance P and enkephalin distribution in rat brain: an overview using radioimmunocytochemistry

The distribution of substance P and leucine enkephalin in mid- and fore-brain areas of the rat was studied using a radioimmunocytochemical method. The secondary antibody was labeled with 125I and the sections apposed to LKB Ultrofilm or emulsion-dipped. In alternate sections an extensive distribution of substance P and enkephalin immunoreactive material was seen in frontal, cingulate, retrosplenial, and entorhinal cortices. Substance P and enkephalin exhibited a remarkable overlap in many of these cortical areas as well as in the nucleus accumbens, caudate, portions of the hypothalamus, amygdala, thalamus and central gray. Differences in distribution were seen in the retrosplenial cortex, septum, ventromedial hypothalamus, hippocampus, the substantia nigra and the superior colliculus. The results provide a detailed immunohistochemical demonstration of the laminar patterns of substance P and enkephalin in the cortex of the rat. The results are discussed in terms of the interaction of substance P and enkephalin. The matches and mismatches of immunoreactive substance P and enkephalin and the locations of their receptors are also examined.

Cholecystokinin innervation of the ventral striatum: a morphological and radioimmunological study

Immunocytochemistry, radioimmunological assay after surgical cuts, anterograde degeneration and retrograde tracing of fluorescent dyes were used in order to elucidate the cholecystokinin-containing afferents to the ventral striatum (nucleus accumbens, olfactory tubercle and ventral part of the caudate-putamen). In agreement with the report by Hökfelt et al., midbrain cholecystokinin-containing cells supply the posteromedial parts of the nucleus accumbens and olfactory tubercle, as well as the subcommissural part of caudate-putamen. Brainstem cholecystokinin afferents also reach more rostral parts of the ventral striatum including the rostrolateral olfactory tubercle. The ascending cholecystokinin axons enter the medial forebrain bundle at the meso-diencephalic border and maintain a rough medial to lateral topography at the caudal diencephalon. A second major cholecystokinin pathway, with possible origin in the piriform and medial prefrontal cortices and/or the amygdala, projects to the subcommissural caudate-putamen, the olfactory tubercle, the lateral part of the nucleus accumbens and the dorsal part of the bed nucleus of stria terminalis. Finally, the rostral part of the dorsal caudate-putamen receives a substantial cholecystokinin innervation from the basolateral amygdala and possibly from the neocortex. According to radioimmunological data, the descending telencephalic cholecystokinin system accounts for about 60% of all cholecystokinin in the rostral forebrain. The combined use of morphological and biochemical methods provided evidence for a partially overlapping distribution and possible interaction between an ascending brainstem and descending telencephalic cholecystokinin fiber systems within the striatum and related rostral forebrain areas.

Behavioral analysis of the effect of substance P injected into the ventral mesencephalon on investigatory and spontaneous motor behavior in the rat

In the present experiments the behavioral response to substance P (SP) microinfusion into the ventral tegmental area (VTA), substantia nigra (SN), and sensorimotor cortex (CX) was investigated in detail. The experiments were carried out using an eight-hole box to measure exploratory behavior and a video monitor for the analysis of spontaneous motor behavior. When infused into the VTA, SP (0.125, 0.5, 3.0 micrograms) augmented the frequency and total duration of hole-pokes, and tended to diminish the mean duration of hole-pokes. The strategy and organization of responses, as measured by the order of hole-visits and hole-switching, were unchanged by SP and there was no indication of stereotypy, measured by the number of hole-pokes per hole-visit. The open-field analysis revealed a marked increase in locomotion and rearing, both in the periphery and center of the arena; grooming was decreased by SP. The behavioral profile following SN infusions of SP (3.0 micrograms) was similar to that elicited by VTA infusions, with the exception that center rearing was not enhanced. SP administration into cortex (3 micrograms) had no significant effect on any behavioral measures. It is hypothesized that SP infused into the ventral mesencephalon results in an enhancement of approach response tendencies, suggesting that endogenous SP in this region may regulate spontaneous behavior. The possibility of an interaction between SP and meso-telencephalic dopamine neurons is discussed.

Neuropeptide Y in the stria terminalis: evidence for an amygdalofugal projection

Lesions of the stria terminalis in the rat brain indicate that neuropeptide Y, a recently isolated peptide of the pancreatic polypeptide family, projects rostrally in an efferent pathway from the amygdaloid complex. Marked depletions of NPY-immunoreactivity observed by immunocytochemistry were apparent in the laterobasal septum and suprachiasmatic nucleus of the hypothalamus, but most markedly in rostrolateral regions of the bed nucleus of the strial terminalis.

Influence of ascending noradrenergic fibers on the neurotensin-like immunoreactive perikarya and evidence of direct projection of ascending neurotensin-like immunoreactive fibers in the rat central nucleus of the amygdala

The influence of ascending noradrenergic neuronal input on the neurotensin (NT)-like immunoreactive neuronal perikarya located in the dorsal part of the central nucleus of the amygdala (CNA) was examined using fluorescence histochemistry and peroxidase-antiperoxidase (PAP) immunocytochemistry. Unilateral hemitransection of the ascending noradrenergic pathway by injection of 6-hydroxydopamine into the caudal mesencephalon just rostral to the locus coeruleus caused a marked depletion of immunoreactivity in NT-like immunoreactive neuronal perikarya in the CNA. Ascending noradrenergic neuronal input, therefore, is considered to facilitate production of NT-like immunoreactive substances in neuronal perikarya and to influence on the functional role of the amygdaloid complex. In addition, we obtained evidence of unilateral direct ascending projections of NT-like immunoreactive neurons into the CNA since the disappearance of NT-like immunoreactive processes occurred mainly in the ventral part of the CNA after surgical hemitransection of the ascending neuronal pathway that interrupts the ascending NT-like immunoreactive pathway arising from the neurons in the brain stem.

Immunohistochemical distribution of somatostatin-like immunoreactivity in the central nervous system of the adult rat

The localization and distribution of somatostatin (growth hormone release-inhibiting hormone; somatotropin release-inhibiting factor) have been studied with the indirect immunofluorescence technique of Coons and collaborators and the immunoperoxidase method of Sternberger and coworkers using specific and well-characterized antibodies to somatostatin, providing semiquantitative, detailed maps of somatostatin-immunoreactive cell profiles and fibers. Our results demonstrate a widespread occurrence of somatostatin-positive nerve cell bodies and fibers throughout the central nervous system of adult, normal or colchicine-treated, albino rats. The somatostatin cell bodies varied in size from below 10 micron up to 40 micron in diameter and could have only a few or multiple processes. Dense populations of cell somata were present in many major areas including neocortex, piriform cortex, hippocampus, amygdaloid complex, nucleus caudatus, nucleus accumbens, anterior periventricular hypothalamic area, ventromedial hypothalamic nucleus, nucleus arcuatus, medial to and within the lateral lemniscus, pontine reticular nuclei, nucleus cochlearis dorsalis and immediately dorsal to the nucleus tractus solitarii. Extensive networks of nerve fibers of varying densities were also found in most areas and nuclei of the central nervous system. Both varicose fibers as well as dot- or "dust-like" structures were seen. Areas with dense or very dense networks included nucleus accumbens, nucleus caudatus, nucleus amygdaloideus centralis, most parts of the hypothalamus, nucleus parabrachialis, nucleus tractus solitarii, nucleus ambiguus, nucleus tractus spinalis nervi trigemini and the dorsal horn of the spinal cord. One exception is the cerebellum which only contained few somatostatin-positive cell bodies and nerve fibers. It should be noted that somatostatin-positive cell bodies and fibers did not always conform to the boundaries of the classical neuroanatomical nuclei, but could often be found in areas between these well-established nuclei or occupying, in varying concentrations, only parts of such nuclei. It was difficult to identify with certainty somatostatin-immunoreactive axons in the animals studied. Some pathways could, however, be demonstrated, but further experimental studies are necessary to elucidate the exact projections of the somatostatin-immunoreactive neurons in the rat central nervous system.

Quantitative electron microscopic study of immunoreactive somatostatin axons in the rat neostriatum

Various features of immunoreactive somatostatin axons including bouton size, synaptic length, the type of synapse formed (symmetric or asymmetric) and postsynaptic target, were examined at the ultrastructural level in the caudate nucleus. These features were compared to those of unlabeled axons in the surrounding caudate neuropil. Results showed that immunoreactive somatostatin axons make relatively short-surfaced, symmetric contacts, mostly with dendritic shafts whereas the majority of unlabeled axons form long-surfaced, asymmetric synapses with dendritic spines. Observations indicate that immunoreactive somatostatin axons belong to a sparse and homogeneous population of axons, have features corresponding to those of intrinsic caudate neurons, and synapse with caudate spiny cells. These findings are consistent with earlier speculation that immunoreactive somatostatin axons in caudate arise from a population of aspiny interneurons which have previously been identified to contain the peptide.

Distribution of pro-opiomelanocortin-derived peptides and enkephalins in the rat central nucleus of the amygdala

The distribution and origin of beta-endorphin (BE) and alpha-melanocyte stimulating hormone (alpha-MSH) terminals was studied in the central nucleus of the rat amygdala (CNA). The distributions of BE and alpha-MSH within the CNA were compared to that of Met- and Leu-enkephalin (ENK). BE and a-MSH terminals were found mainly in the medial subdivision of the CNA, and originated, at least in part, from the arcuate nucleus region of the hypothalamus. ENK terminals were found in both the medial and lateral subdivisions of the CNA, although a considerably higher density of terminals was seen within the lateral subdivision. This differential distribution of proopiomelanocortins and ENKs may reflect different functions for these endogenous opiates in the CNA.

Innervation of human bone periosteum by peptidergic nerves

Nerves exhibiting substance P-like immunoreactivity were demonstrated in the human periosteum. A network of nerves showing substance P-like immunoreactivity was seen in the periosteum, while finer strands of immunoreactive nerve fibers were present immediately beneath the surface of the periosteum. Enkephalin-like immunoreactivity was also studied but could not be demonstrated. Substance P has previously been suggested to be involved in the mediation of the sensation of pain. The clinically observable marked pain sensitivity of periosteal tissue might be explained by the peptidergic nerves described in this paper.

The organization of projections from the central nucleus of the amygdala to brainstem sites involved in central autonomic regulation: a combined retrograde transport-immunohistochemical study

The central nucleus of the amygdala (ACe) in the rat sends a considerable projection to, and receives projections from, the parabrachial nucleus (PB) and the dorsal vagal complex (DVC; the nucleus of the solitary tract and the dorsal motor nucleus of the vagus nerve). In each part of this 'triangle', immunohistochemical staining for the following peptides has been observed in perikarya and fibers: neurotensin, somatostatin, substance-P, Leu-enkephalin and corticotropin-releasing factor. The aim of the present study was to investigate whether any of these peptides are involved in projections to the brainstem from the ACe, and to characterize the distribution of each cell type in the ACe. The results of double retrograde tracing studies indicate that most of the ACe neurons projecting to the PB and DVC are present in the medial part of ACe (ACem), and that many of them project to both the 1 B and the DVC. The combined use of immunohistochemistry with a retrograde fluorescent tracer, True Blue, indicated that the peptide-containing perikarya are found predominantly in the lateral part of ACe (ACe1), and that only a small proportion of neurotensin, somatostatin and corticotropin-releasing factor-stained neurons contained True Blue after injections into the PB or the DVC. The results suggest that most of the fibers in the descending projection from the ACe to the brainstem do not contain the peptides examined here.

Cholecystokinin-8-like immunoreactivity in the rat anterior commissure revealed by immunocytochemistry

The present experimental immunohistochemical study demonstrated that one of the major components of the anterior commissure of the rat is the cholecystokinin-8-like immunoreactivity ( CCKI )-containing fiber system. We further showed that these fibers reached the contralateral side and dissociated into CCKI fibers in the ipsi- and contralateral anterior limbs.

Neuronal organization of the lateral and basolateral amygdaloid nuclei in the rat

The neuronal organization of the lateral (L) and basolateral (BL) amygdaloid nuclei was studied in the rat by using Golgi techniques. All nuclear subdivisions, which were identified in Nissl and acetylcholinesterase preparations, contain spiny class I neurons and spine-sparse class II neurons. Three of four neurogliaform class III neurons observed were located in the anterior division of BL (BLa). The exact arrangement of class I and class II neurons varies in different portions of L and BL. At the periphery of these nuclei, where L and BL border fiber bundles, major dendrites tend to be oriented parallel to nuclear borders. Many smaller dendritic branches, however, may extend into the adjacent fiber bundles. At most borders between nuclear subdivisions dendritic overlap is minimized by the fact that major dendrites tend to run parallel to subdivisional boundaries. One exception is the junction of BLa with the posterior division of BL (BLp), where unrestricted dendritic overlap of both class I and class II neurons occurs. Within most nuclear subdivisions dendrites of class I and class II neurons ramify freely and exhibit little order. In caudal portions of BLp, however, almost all class I neurons are pyramidal cells with vertically oriented apical dendrites. Dendrites of class II neurons in this region tend to be oriented horizontally, perpendicular to apical dendrites of class I cells. Class II neurons were not evenly distributed in Golgi preparations but were concentrated at the BLa-BLp border, near the boundary between the dorsolateral and ventromedial subdivisions of L and in the dorsal portion of BLp. The latter cells blend with similar spine-sparse neurons contained within the external capsule. Analysis of Nissl preparations reveals that small neurons, which correspond to small class II and class III cells, are sometimes observed in a clustered arrangement.

The distribution and ultrastructure of VIP-immunoreactivity in the central nucleus of the rat amygdala

Vasoactive intestinal polypeptide (VIP) neurons within the central nucleus of the rat amygdala were examined using light and electron microscopic immunocytochemical techniques. Vasoactive intestinal polypeptide-immunoreactive neurons were located in the ventral part and less frequently in the central part of the central nucleus. Vasoactive intestinal polypeptide positive terminals were distributed throughout the medial part of a cytoarchitectonically distinct central zone of the central nucleus. Three types of terminals formed synaptic contacts on VIP-immunoreactive neurons: type A containing round vesicles, type B containing many pleomorphic vesicles and type C containing fewer pleomorphic vesicles. All VIP-immunoreactive boutons observed were of type A variety, and made asymmetrical and symmetrical synaptic contacts on both VIP-immunoreactive and nonreactive neurons within the central nucleus.

Projections of the amygdala to the thalamus in the cynomolgus monkey

The projections of the amygdala to the thalamus in cynomolgus monkeys (Macaca fascicularis) were studied with both anterograde and retrograde axonal tracing techniques. Horseradish peroxidase (HRP) was injected into medial and midline thalamic sites in five animals, and tritiated amino acids were injected into selected amygdaloid regions in a total of 13 hemispheres in ten animals. The findings from the two types of tracer experiments demonstrated the origins, course, and terminal pattern of amygdaloid projections to two thalamic nuclei--medialis dorsalis (MD) and reuniens. Almost all of the amygdaloid nuclei contribute projections to MD, though the greatest proportion arise from the basal group and terminate in discrete, interlocking patches within the medial, magnocellular portion of MD. In addition to this major projection, the central and medial amygdaloid nuclei send a lighter projection to the lateral portion of nucleus reuniens. The amygdalothalamic projections took a variety of routes out of the amygdala before the large majority joined the inferior thalamic peduncle and entered the rostral head of the thalamus where they turned caudally toward their targets. A small number of amygdalothalamic fibers may also run in the stria terminalis.

Distribution of neuropeptides in the limbic system of the rat: the hippocampus

The distribution of several neuropeptides (vasoactive intestinal polypeptide, cholecystokinin octapeptide, substance P, neurotensin, methionine-enkephalin and somatostatin) in the hippocampal formation has been studied with immunocytochemical techniques. Numerous vasoactive intestinal polypeptide, cholecystokinin-octapeptide and somatostatin-positive cell bodies were found within the hippocampus and subiculum. Neurotensin-positive cell bodies were found within the subiculum, but no substance P or methionine-enkephalin-containing cell bodies were seen in either hippocampus proper or subiculum. Vasoactive intestinal polypeptide and cholecystokinin-octapeptide-positive cell bodies were predominantly located in the stratum moleculare and stratum radiatum of CA 1-2 regions and dentate gyrus, whilst somatostatin-containing cell bodies were found mainly in the stratum oriens. Nerve fibres containing each of the six peptides were found within the hippocampus. Large numbers of vasoactive intestinal polypeptide, cholecystokinin-octapeptide and somatostatin fibres innervated the pyramidal and granule cell layers, with smaller numbers in the stratum radiatum and fewer still in the stratum moleculare and stratum oriens. Other than a moderately dense neurotensin-positive fibre plexus in the dorsal subiculum, fewer neurotensin, substance P and methionine-enkephalin fibres were present. However, when present, these three peptides had a distribution restricted to a region close to the pyramidal layer in the CA 2/3 region and to the stratum moleculare of the CA 1 region. Peptide-containing fibres were identified entering or leaving the hippocampus in three ways, via (i) the fornix (all six peptides), (ii) the dorsal subiculum (neurotensin-positive fibres projecting to the cingulate cortex: somatostatin, vasoactive intestinal polypeptide, and cholecystokinin-octapeptide present in fibres running between the dorsal subiculum and occipito-parietal cortex) and (iii) the ventral subiculum (vasoactive intestinal polypeptide, cholecystokinin-octapeptide and somatostatin in fibres running between entorhinal cortex and hippocampus, and all six peptides in fibres crossing the amygdalo-hippocampal border). These findings indicate a major distinction between those peptides (vasoactive intestinal polypeptide, cholecystokinin-octapeptide, somatostatin, neurotensin) which are found in cell bodies intrinsic to the hippocampal formation and those peptides (substance P, methionine-enkephalin) which are found only in hippocampal afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

Peptides, the limbic lobe and schizophrenia

The human brain contains several peptides with probable synaptic actions, some of which form complex neuronal networks in the limbic lobe (amygdala, hippocampus and temporal cortex). A limbic lobe abnormality has been postulated in schizophrenia on the basis of similarities between schizophrenic symptoms and symptoms in cases of known limbic pathology. Cholecystokinin (CCK), somatostatin (SRIF), neurotensin (NT), vasoactive intestinal polypeptide (VIP) and substance P (SP)-like immunoreactivities were measured by radioimmunoassay in 10 brain areas of 14 schizophrenics and 12 controls. In the schizophrenic group symptoms had been rated in life and the group was divided into Type I (n = 7) and Type II (n = 7) subgroups on the basis of the absence or presence of morbid negative symptoms. In control brains each peptide showed a characteristic distribution with high levels in cortex (CCK), limbic lobe (SOM, NT, VIP) or striatal areas (SP) and low levels of each of the peptides in thalamus. Significant (P less than 0.05) differences between groups were: reductions of CCK and SOM in hippocampus and CCK in amygdala in Type II schizophrenics, and CCK in the temporal cortex of the total schizophrenic group; and elevations of VIP in amygdala in Type I schizophrenics and of SP in the hippocampus in the total schizophrenic group. The findings could not be explained by variables such as age, delay between death and necropsy or to neuroleptic medication. These clinical-state related alterations in the peptide content of the limbic system in schizophrenia may illuminate the pathophysiological basis of the disease, particularly the distinction between Type I and II syndromes.

Neuropeptide Y distribution in human brain

Tatemoto and Mutt recently used the presence of a C-terminal NH2 group to identify and isolate a new peptide, neuropeptide Y (NPY), from porcine brain. This 36 amino acid peptide was subsequently shown to be active on isolated vas deferens, vascular smooth muscle and pancreatic acinar cells in very low molar concentrations. In view of these potent effects we have now investigated its distribution in the human brain by radioimmunoassay and immunocytochemistry. High concentrations of NPY have been found, exceeding those of cholecystokinin and somatostatin, hitherto considered to be the most abundant neuropeptides. The distribution of NPY was different from that of any other peptide system described, being particularly concentrated in the basal ganglia, amygdala and nucleus accumbens. Immunocytochemistry demonstrated a large number of NPY neuronal cell bodies especially in the caudate and putamen. Immunoreactive neuronal cell bodies were also clearly localized in cortical areas, particularly layers V and VI. NPY, a newly discovered peptide with potent biological activity, thus seems to be among the most abundant of human neuropeptides. The massive numbers of NPY neurones in the basal ganglia suggest NPY to be of fundamental importance in the control of human motor function.

Neuronal configurations in lateral and basolateral amygdala

The lateral and basolateral nuclei of the rat amygdala have been studied with the rapid Golgi method. Both nuclei have similar cell types, which closely resemble cells in the cerebral cortex. Therefore, we suggest that what is known about cortical circuitry can be used as a guide for studying synaptic circuitry in the lateral and basolateral nuclei. The most abundant neurons that are impregnated in both nuclei are pyramidal cells. They have conical cell bodies and easily recognizable apical and basilar dendrites. The ones in the center of each nucleus have long axes that roughly parallel the long axis of the nucleus. Towards the periphery, pyramidal cells have apical dendrites that either stick directly across the nucleus or follow along a nuclear border. The peripheral dendrites tend to enclose the nuclei. There is considerable overlap among the dendritic trees and the dendrites of one nucleus extend into the territory of the other. Pyramidal cells have extensive axonal systems. The principal axon of basolateral cells usually projects rostrally but long collaterals leave the nucleus in other directions. The axons of lateral nucleus pyramidal cells are also widely distributed. The major thrust of their axons is caudal and lateral. Stellate cells are the most common variety of the non-pyramidal cells. They occur in both nuclei and have round cell bodies, 10-15 micron diameter, and spherical dendritic trees that are confined to a limited region of the nucleus. Their axons form dense terminal fields that remain within the vicinity of the parent cell's dendritic tree. Another type of non-pyramidal cell is the cone cell, whose non-spiny, varicose dendrites describe cones. These neurons are found mainly in the apex of the lateral nucleus. The most rare non-pyramidal cells are the extended neurons, which have long, straight dendrites that reach beyond the nucleus into surrounding neuropil. They are mostly in the rostral part of the basolateral nucleus but also occur in the lateral nucleus, near the ventricular border. The axons of cone cells and the extended neurons have been only partially impregnated. We also have examined stellate cells in the guinea-pig lateral and basolateral nuclei. They have many of the same features as those in the rat brain, except that their dendritic trees and axonal systems are more complicated. There are two large groups of afferents: one consists of longitudinally running axons and the other of transversely coursing fibers.(ABSTRACT TRUNCATED AT 400 WORDS)

The morphology of somatostatin-immunoreactive neurons in the lateral nucleus of the rat amygdala

Three types of somatostatin-immunoreactive neurons are described in the lateral nucleus of the rat amygdala. These three types closely correspond to neurons previously reported in Golgi preparations of the lateral nucleus. Class I somatostatin neurons have triangular- or piriform-shaped somata with large primary dendrites and spiny secondary dendrites. Class II somatostatin neurons have small to medium-sized oval perikarya and are fusiform or multipolar in shape. Class III somatostatin neurons have small spheroid somata with small thinner relatively aspinous dendrites. Class I somatostatin neurons give rise to axons which project outside the lateral nucleus whereas class II and III neurons innervate other somatostatin-positive and non-somatostatin neurons within the lateral nucleus. Somatostatin neurons within the lateral nucleus are hypothesized to function as part of a network of somatostatin neurons extending from cortical regions through the amygdala to basal telencephalic and lower brain stem regions.

Neuronal types in the basolateral amygdaloid nuclei of man

A parcellation of the human basolateral amygdala is given on the basis of pigmentoarchitectonic analysis. Examination of Golgi preparations and deimpregnated preparations counterstained for lipofuscin pigment revealed three classes of nerve cells: Class I neurons generate a stout main dendrite from one pole of the cell body and several minor ones from the base opposite to the main process. The dendrites are covered with spines. The axon follows a straight course and gives off numerous collaterals. Class I neurons in the lateral and accessory basal nucleus contain finely granulated and widely dispersed pigment. Cells located in the basal nucleus store a large amount of pigment, concentrated at one pole of the cell body. The small class I neurons in the granular nucleus and the intercalated cell masses are marked by large vacuolated pigment granules. Class II neurons have smoothly contoured or sparsely spined dendrites. Size and shape of their cell bodies vary. They contain a large amount of course and intensely stained lipofuscin granules. Class III neurons display similar features in the Golgi preparation but their cell bodies are devoid of pigment. A frequently occurring type is a tiny cell with thin dendrites and profusely branching local axon. Each of the different classes of neurons shows a characteristic pattern of pigmentation. Therefore, Nissl preparations combined with a pigment staining technique, offer the particular advantage of distinguishing the spine-laden neurons from sparsely spined or aspinous types.

Somatostatinergic projections from the central nucleus of the amygdala to the vagal nuclei

In the rat, somatostatin immunoreactivity was identified in neurons of the central nucleus of the amygdala that were retrogradely labeled by injection of fluorescent dyes into the nucleus tractus solitarius and dorsal motor nucleus of the vagus nerve. The double-labeled neurons are located in the medial subdivision of the central nucleus and appear to comprise less than one fifth of the descending pathway. These results suggest that somatostatin may act as a neurotransmitter in a pathway which mediates cardiovascular and other autonomic responses to fear-producing and other emotional stimuli.

Distribution and origins of neurotensin-containing fibers in the nucleus ventromedialis hypothalami of the rat: an experimental immunohistochemical study

The distribution and origins of neurotensin (NT)-containing fibers in the nucleus ventromedialis hypothalami (VM) of the rat were investigated experimentally using an indirect immunofluorescence technique. A dense plexus of NT-like immunoreactive (NTI) fibers which was composed of very fine varicosities was identified in the VM. Although they were distributed throughout its entire rostrocaudal extent, the distribution was uneven. The highest density was identified in the dorsomedial part of the VM. In the central part, a less numerous but still moderate number of NTI fibers was detected in its dorsal part. But in a ventrolateral direction, they decreased in number and in the ventrolateral part only a few NTI fibers were seen. The present study demonstrated experimentally that these fibers originate from the medial nucleus of the amygdaloid complex (AM), since destruction of the AM resulted in a marked reduction of NTI fibers ipsilaterally in the VM. These findings suggest that the AM influences the VM's functions via neurotensin-like immunoreactive fibers.

Reduced cholecystokinin-like and somatostatin-like immunoreactivity in limbic lobe is associated with negative symptoms in schizophrenia

Cholecystokinin-like immunoreactivity (CCK) and somatostatin-like immunoreactivity (SRIF) were determined in fourteen brains from patients dying with a diagnosis of schizophrenia and in twelve brains from control cases. The schizophrenics had been rated during life and were divided into two groups on the basis of the presence or absence of negative symptoms (affective flattening and poverty of speech). CCK was reduced in temporal cortex of the schizophrenics and in hippocampus and amygdala of those patients with negative symptoms. SRIF was reduced in the hippocampus in samples from the latter group. The selectivity of these changes to limbic lobe may reflect the presence of a degenerative process in that area. The association of changes in hippocampus and amygdala with negative symptoms of schizophrenia suggests a separate mechanism underlying these symptoms.

Ontogeny of cholecystokinin-8-containing neuron system of the rat: an immunohistochemical analysis. I. Forebrain and upper brainstem

Ontogeny of the cholecystokinin-8 (CCK) neuron system in the forebrain and upper brainstem of the rat was investigated by means of indirect immunofluorescence. CCK cells and fibers first appeared in the developing ventral tegmental area and in the primordium of the medial forebrain bundle, respectively, at gestational day 15 (12-14-mm embryos). From that time, CCK cells appeared in various areas of the forebrain and upper brainstem until birth and reached the maximum content at postnatal day 10. After postnatal day 10, although CCK cells tended to decrease slightly in number, colchicine treatment in the adult rats brought out numerous CCK cells in the same areas. In contrast, although CCK fibers developed only slightly during the fetal period, marked development was seen after birth, particularly between postnatal days 5 and 10. After that time, as the rats grew, CCK fibers continued to increase in number and formed a meshwork of varying density in various areas of the forebrain and upper brainstem.

Naloxone attenuates amnesia caused by amygdaloid stimulation: the involvement of a central opioid system

This study investigated the effect of naloxone on amnesia produced by subseizure amygdaloid stimulation. Animals were trained in an inhibitory avoidance task, and given amygdaloid stimulation following training. Immediately after training, prior to stimulation, naloxone was injected either peripherally (i.p.) or into the bed nucleus of the stria terminalis (BNST) where the Met-enkephalin-containing fibers from the amygdala terminate. Amygdaloid stimulation caused retention deficits. The deficits were attenuated by 3.0 mg/kg naloxone given peripherally or by 1.0 microgram or 0.3 microgram naloxone injected bilaterally into the BNST. The attenuative effect was anatomically and receptor specific: 0.3 microgram of naloxone injected into the caudate nucleus was ineffective; the attenuative effect of naloxone was antagonized by simultaneous injection of 1.5 or 4.5 micrograms levorphanol into the BNST. These results suggest that endogenous opioids, possibly the enkephalins of the stria terminalis released into the BNST following amygdaloid stimulation, are at least partially involved in mediating the effect of amygdaloid stimulation on memory.

Organization and interrelationship of neuropeptides in the central amygdaloid nucleus of the rat

The organization and interactions of neuropeptides in the central nucleus of the amygdala (Ce) were studied using single and double label immunocytochemical techniques. Immunocytochemical localization of substance P (SP), neurotensin (NT), met-enkephalin (m-ENK), somatostatin (SS) and vasoactive intestinal polypeptide (VIP) revealed all of these peptides within discrete regions of the Ce. The regions differed from the classical medial and lateral anatomical divisions reported for the Ce. Instead, three easily recognizable neuropeptidergic subdivisions were evident: a medial zone, a central zone and a lateral capsular zone. Two types of interrelationships between peptides were noted. The first involved a peptidergic fiber in apposition to a peptidergic perikarya. The most prevalent peptidergic interaction of this type occurred between SP and NT. The second interrelationship involved two different peptidergic fibers in apposition to an immunonegative cell. Two interactions of this type were commonly observed. The first involved NT and m-ENK fibers simultaneously apposed to an unstained cell. The second involved SP and m-ENK fibers adjacent to the same immunonegative cell. The interactions between peptidergic systems may suggest a role of these substances in the regulation of autonomic functions in the Ce.

Distribution of enkephalin-related peptides in rat brain: immunohistochemical studies using antisera to met-enkephalin and met-enkephalin Arg6Phe7

The enkephalin-related heptapeptide, Tyr-Gly-Gly-Phe-Met-Arg-Phe, forms the C-terminus of a biosynthetic precursor that contains both Met-enkephalin and Leu-enkephalin sequences. We have studied the distribution of heptapeptide-like immunoreactivity in rat brain by immunohistochemistry using a C-terminal specific antiserum. The results were compared with those obtained using an antiserum specific for the C-terminus of Met-enkephalin which does not react with C-terminally-extended variants. Both antisera specifically stained cell bodies and fibres in many regions of the rat central nervous system. Colchicine was needed for the demonstration of cell bodies with the Met-enkephalin antiserum, but not for the heptapeptide antiserum. In the nucleus of the solitary tract, in the commissural nucleus, the nucleus raphe obscurus and in the hypothalamus, studies of serial sections and re-staining experiments indicated that the two antisera stained the same cell bodies. However, in the olfactory bulb, the anterior olfactory nucleus, the olfactory tubercle, the nucleus accumbens, caudate-putamen, central nucleus of the amygdala, nucleus interstitialis striae terminalis, pre-lateral mamillary nuclei, ventral hypothalamus, hippocampus, peri-aqueductal grey and the granular layer of the cerebellum, cells were stained by the heptapeptide antiserum but not the Met-enkephalin antiserum. The two antisera revealed similar patterns of staining of nerve fibres in many regions including hypothalamus, central nucleus of the amygdala, lateral septum, thalamus, mid-brain and spinal cord. But in other areas notably, pallidum, caudate-putamen, substantia inominata, nucleus of the solitary tract and commissural nucleus, there were abundant fibres and terminals revealed by the Met-enkephalin antiserum but not by the heptapeptide antiserum. The results are discussed with respect to possible patterns of enkephalin biosynthesis; it is suggested that in some neurones immunoreactive enkephalin precursors terminating in the heptapeptide sequence are processed to produce the heptapeptide which is stored in terminals and is available for release as an endogenous opioid agonist in its own right. In other cases, however, it is suggested that the heptapeptide might be cleaved by removal of -Arg-Phe to yield Met-enkephalin which is the primary opioid product of this class of neurone.

Changes of immunoreactive somatostatin and beta-endorphin content in rat brain after amygdaloid kindling

A possible contribution of brain beta-endorphin and somatostatin to the epileptogenicity established by amygdaloid kindling was investigated in rats. Fourteen male rats were chronically implanted with electrodes placed bilaterally into the amygdala. The rats received 1 sec of electrical stimulation to the left amygdala each day. Generalized seizures were observed on average 10 days after initiation of kindling and the electrical stimulation was continued up to twenty-one days. Two months after the completion of the kindling procedure, each kindled and control rat was killed by microwave irradiation and the brains were dissected on ice into thirteen subregions. Each region was homogenized and centrifuged twice in 0.1 N acetic acid. The supernatant extracts were decanted and stored at - 20 degrees C until assay. Immunoreactive beta-endorphin and somatostatin were measured by radioimmunoassays. There were no significant differences in brain beta-endorphin contents between the two groups. In kindled rats, immunoreactive somatostatin was increased significantly in amygdala, sensorimotor, piriform, and entorhinal cortex. The results suggest that changes in somatostatin may be associated with epileptic susceptibility induced by the electrical kindling procedure.

Distribution of the VIP-like immunoreactive neurons in the cat central nervous system

Immunohistochemical topographic localization of the vasoactive intestinal polypeptide (VIP)-like immunoreactive neurons in the cat brain was investigated using a peroxidase anti-peroxidase technique. VIP-like immunoreactive neurons were mainly localized in the cerebral cortex, limbic cortex, hypothalamic nuclei; suprachiasmatic nucleus, supraoptic nucleus, paraventricular nucleus, periventricular nucleus and arcuate nucleus, and in the midbrain; such as the central grey and the raphe nucleus. It was demonstrated that VIP-like immunoreactive neurons were widely distributed in the cat brain, particularly in the hypothalamus, compared with those of the rat and mouse; though whether these differences were species-related or due to differences in the physiological conditions remains to be determined. This is the first report of VIP neuronal perikarya in the arcuate nucleus of mammalian species, although these cells are present in the arcuate nucleus of birds.

Distribution of neuropeptides in the limbic system of the rat: the bed nucleus of the stria terminalis, septum and preoptic area

The distribution of the neuropeptides vasoactive intestinal polypeptide, cholecystokinin octapeptide, substance P, neurotensin, methionine-enkephalin and somatostatin has been mapped immunocytochemically in the bed nucleus of the stria terminalis, one of the major sites of termination for efferent projections from the amygdala. Immunoreactive fibres and terminals were distributed more or less topographically and largely in accordance with the previously described localization of peptide-containing cell bodies in the amygdala and the amygdaloid projection fields in the bed nucleus as described by neuroanatomical techniques. Thus, vasoactive intestinal polypeptide, which was found in some of the lateral amygdaloid nuclei, had a substantial projection to the lateral bed nucleus. The lateral bed nucleus also contained cholecystokinin-octapeptide, substance P, neurotensin and methionine-enkephalin immunoreactivity which probably derived from the central amygdaloid nucleus, whilst cholecystokinin-octapeptide, and especially substance P-containing fibres, were found in the medial bed nucleus and probably arise from cells in the medial amygdala. Reciprocal amygdalopetal projections were suggested by the presence of substance P- and somatostatin-containing cell bodies in the mediodorsal bed nucleus and vasoactive intestinal polypeptide cells in the lateral bed nucleus, but somatostatin otherwise had a widespread distribution. Numerous local peptidergic connections were also noted both within the bed nucleus and between it and adjacent structures, especially the preoptic area, hypothalamus and the basal ganglia. These data provide further evidence that neuropeptides play a major role in the connectivity of the limbic system and show that the bed nucleus of the stria terminalis is an important relay station, particularly between amygdaloid efferents and other forebrain areas.

Immunocytochemical localization on neuropeptides in the fornix of rat, monkey and man

Using specific antisera and immunocytochemical methods VIP, CCK, substance P, methionine-enkephalin, neurotensin and somatostatin-like immunoreactive fibers were found within the fornix and fimbria in 3 species (rat, monkey and human). Neither methionine-enkephalin- nor substance P-containing cell bodies were located within the hippocampus and so fibers containing these peptides are presumably hippocampal afferents, probably arising in the septum or caudal hypothalamus. VIP, CCK, neurotensin and somatostatin fibers may be hippocampal efferents arising from cell bodies within the subiculum.

Evidence for the existence of a neurotensin-containing pathway from the endopiriform nucleus and the adjacent prepiriform cortex to the anterior olfactory nucleus and nucleus of diagonal band (Broca) of the rat

The origin of neurotensin-like immunoreactive fibers to the anterior olfactory nucleus and nucleus of the diagonal band of Broca of the rat were elucidated experimentally using the indirect immunofluorescence method. Neurotensin-like immunoreactive fibers located in these areas decreased remarkably in numbers on the operated side after the destruction of the ventral part of the endopiriform nucleus and the adjacent prepiriform cortex where numerous cells with neurotensin-like immunoreactivity were detected. This strongly suggests that such cells located in the endopiriform nucleus and the adjacent prepiriform cortex send a neurotensin-like projection ipsilaterally to the anterior olfactory nucleus and to the nucleus of the diagonal band of Broca.

Fine structural studies on a type of somatostatin-immunoreactive neuron and its synaptic connections in the rat neostriatum: a correlated light and electron microscopic study

Somatostatin-immunoreactive neurons in the rat neostriatum were studied by correlated light and electron microscopy using the peroxidase-antiperoxidase immunocytochemical technique. Immunoreactivity was localized in neuronal perikarya and processes. The perikarya were of spindle or fusiform shape (average length 16.9 microns) and were found in all parts of the neostriatum. From each neuron there arose two to four straight immunoreactive dendritelike processes, which could frequently be traced as far as about 130 microns from their perikaryon. Immunoreactive varicose axonlike processes were occasionally found, some of which were proximal axons of identified immunoreactive cells. Nine of the light microscopically identified neurons showing somatostatin-immunoreactivity were studied in the electron microscope; two of them had proximal axons with varicosities. Each neuron had an oval or elongated nucleus, which was always indented. These morphological features correspond well to those of certain "medium-size aspiny" neurons classified by Golgi studies. Although the immunoreactive endproduct was diffusely located throughout the neuron, it was characteristically located in the saccules and large granules (diameter 133 nm) of the Golgi apparatus, and large immunoreactive vesicles of similar size to those in the Golgi apparatus frequently occurred in all parts of axon. Very little synaptic input was found on the perikarya and dendrites of somatostatin-immunoreactive neurons. The perikarya and proximal dendrites received both symmetrical and asymmetrical synaptic input, while the distal dendrites usually received boutons that formed asymmetrical contacts. The somatostatin-immunoreactive boutons contained pleomorphic electron-lucent vesicles (diameter 39.3 nm) and a few large immunoreactive granular vesicles; these boutons always formed symmetrical synapses. Their postsynaptic targets were dendritic shafts, spines, and unclassified dendritic profiles. On the other hand, the varicosities of identified proximal axons of somatostatin-positive neurons did not form typical synapses, since they lacked clusters of small vesicles, but some of them were in direct apposition (via membrane specializations) to unlabelled perikarya or dendrites. It is concluded that somatostatin is a useful marker for a particular type of neuron in the neostriatum. The presence of somatostatin immunoreactivity in synaptic boutons is consistent with the view that somatostatin could be a neurotransmitter in the neostriatum.

Neurons of the bed nucleus of the stria terminalis: a golgi study in the rat

Neuronal morphology in the bed nucleus of the stria terminalis (BST) was studied using Golgi techniques. The principal neurons of the lateral subdivision of BST have ovoid perikarya and 4-5 dendrites that branch several times and exhibit a dense covering of spines. Adjacent to the internal capsule is a small region, termed the "juxtacapsular subdivision" of BST, that consists of small, spiny cells. Neurons of the medial subdivision of BST have ovoid perikarya and 2-3 dendrites that branch sparingly. Dendritic spine density varies from sparse to moderate. Dendrites in the dorsocaudal portion of the medial subdivision extend into a cell-sparse zone adjacent to the lateral ventricle. Cells in the lateral portion of the preoptic continuation of BST have dendrites oriented perpendicular to fibers of the stria terminalis which traverse this area while medially located cells are oriented parallel to fibers of the stria. Axons of BST neurons emit collaterals that arborize modestly near the cell of origin. Neurons in the lateral and medial subdivisions of BST resemble, respectively, cells in the lateral and medial subdivisions of the central amygdaloid nucleus. Neurons in the juxtacapsular subdivision of BST are similar to neurons of the intercalated masses of the amygdala.

Neurons of the lateral and basolateral amygdaloid nuclei: a Golgi study in the rat

Neurons in the lateral and basolateral nuclei of the rat amygdala were studied using Golgi-Kopsch and rapid Golgi techniques. According to differences in perikaryal, dendritic, and axonal morphology, three main neuronal classes are recognized. Class I neurons, the predominant cell type in both nuclei, are large, spiny neurons that vary in size in different subdivisions of the lateral and basolateral nuclei. These neurons often have a pyramidal shape, exhibiting one or two thick "apical" dendrites and several thinner "basal" dendrites. Axons of class I neurons, which appear to pass out of the nucleus of origin, usually give off several collaterals that arborize modestly in the vicinity of the cell. Class II neurons are smaller, ovoid cells that comprise approximately 5% of impregnated neurons. These neurons are characterized by spine-sparse dendrites and fairly dense local axonal arborizations. Class II neurons may be classified as multipolar, bitufted, or bipolar, depending on dendritic branching pattern. Another type of class II neuron, the amygdaloid chandelier cell, is recognized by virtue of its distinctive axon. The chandelier cell axon gives off numerous collaterals that form nestlike entanglements exhibiting clusters of axonal varicosities. Isolated chandelierlike axons of undetermined origin were observed forming multiple contacts with initial segments of class I axons. Several small, spherical class III neurons with short, varicose dendrites were observed. Axons branch profusely to form a dense tangle of collaterals in the vicinity of the cell. Both axons and dendrites establish numerous contacts with class I dendrites. This investigation, the first detailed Golgi study of the basolateral amygdala of the rat, reveals that the cytoarchitecture of this brain region in the rat is basically similar to that of the opossum and other mammals. Morphologic details described in this report should be useful in the interpretation of ultrastructural, immunocytochemical, and electrophysiological studies of the basolateral amygdala.

Cytoarchitecture of the central amygdaloid nucleus of the rat

Since recent studies indicate that distinct neuropeptides and projections are associated with discrete portions of the central amygdaloid nucleus (CN), a detailed investigation of the cytoarchitecture of CN should contribute to an understanding of its organization. Qualitative and quantitative analyses of the rat CN using Nissl, Klüver-Barrera, and Golgi techniques suggests that it consists of four subdivisions. The medial subdivision (CM), which is closely associated with the stria terminalis, is narrow caudally but enlarges near the rostral pole of CN. Most neurons in CM have long dendrites that branch sparingly and have a moderate number of dendritic spines. A smaller number of CM neurons have thick dendrites with virtually no spines. Lateral to CM is the lateral subdivision (CL) which appears round in coronal sections. Neurons of CL have a very dense covering of dendritic spines and resemble medium-size spiny neurons of the striatum. Area X of Hall contains spiny neurons similar to those of CL and spine-sparse neurons that resemble medium-size spine-sparse cells of the striatum. Since area X encapsulates the lateral aspect of CL, it is termed the lateral capsular subdivision (CLC) of CN. The lateral capsular subdivision enlarges rostrally and is divided into dorsal and ventral portions by a laminar extension of the putamen. Near the rostral pole of CN a small region of tightly packed, intensely stained neurons is interposed between CL and CM. Golgi preparations reveal that this intermediate subdivision (CI) of CN contains neurons similar to those of CM. The lateral subdivision, CLC, and CM correspond, in part, to subdivisions recognized in previous Nissl studies. The intermediate subdivision has not been recognized as a distinct subdivision in previous investigations. This is the first Golgi study to recognize differences in neuronal morphology in particular subdivisions of the rat CN. The correlation of Nissl and Golgi preparations has permitted a more accurate determination of the boundaries and total extent of each subdivision than the use of Nissl techniques alone.