Distribution of somatostatin-like immunoreactivity in the monkey amygdala

The distribution of somatostatin-like immunoreactivity was studied in the macaque monkey (Macaca fascicularis) by using primary antisera that recognize somatostatin-28 (S309) or somatostatin-28(1-12) (S320). Somatostatin-immunoreactive neuronal cell bodies were observed in all amygdaloid nuclei and cortical regions. The density of labeled cells varied substantially, however, both within and across the various amygdaloid subdivisions. The highest densities of labeled neurons were observed in layer III of the periamygdaloid cortex, in layers II and III of the medial nucleus, in the magnocellular division of the accessory basal nucleus, and in the medial portion of the lateral nucleus. Many labeled cells were also consistently observed in the caudoventral portion of the lateral division of the central nucleus. Labeled cells were heterogeneous in size and shape ranging from small and spherical to large and multipolar. The density of somatostatin-immunoreactive fibers also varied greatly from region to region and was often inversely related to the density of immunoreactive cells. Highest densities of immunoreactive fibers were observed in the periamygdaloid cortex, medial nucleus, parvicellular division of the accessory basal nucleus, paralaminar nucleus, ventrolateral portion of the lateral nucleus, parvicellular division of the basal nucleus, and the lateral division of the central nucleus. Fibers and terminals in the central nucleus had a coarsely varicose appearance and this pattern of staining was continuous along the trajectory of the central nucleus projection to the bed nucleus of the stria terminalis. The large, immunoreactive varicosities located in this area often appeared to outline dendritic or vascular profiles within the substantia innominata. The lowest levels of somatostatin-immunoreactive fibers were observed in the magnocellular division of the basal nucleus and in the ventromedial portion of the accessory basal nucleus.     

Mapping of cholinergic neurons associated with rat supraoptic nucleus: Combined immunocytochemical and histochemical identification

Recent electrophysiological experiments have suggested that electrical stimulation of an area dorsolateral to the rat supraoptic nucleus (SON) activates a cholinergic pathway to the vasopressin neurons of the SON. As no detailed information is available concerning the distribution and projections of the cholinergic neurons in this area, we have sought to provide this using a combination of choline acetyltransferase (ChAT) immunocytochemistry and acetylcholinesterase (AChE) histochemistry. In some cases, these techniques were applied to the same neurons. Almost all neurons just outside of the SON that showed ChAT-like immunoreactivity also stained densely for AChE. These cells were distributed in a region dorsolateral to the SON. Light, punctate AChE staining around SON neurons was observed predominantly in the more ventral and posterior parts of the nucleus and were suggestive of synaptic terminals. Cholinergic fibres were found to enter the SON mainly from a lateral direction, turning in an anterior or posterior direction inside the nucleus. These results support the conclusion of earlier studies that the major cholinergic input to the SON arises in its immediate vicinity. We hypothesize that these ChAT/AChE-positive neurons are those responsible for cholinergically mediated, osmotically-stimulated release of vasopressin.     

Pattern of selected calcium-binding proteins in the vestibular nuclear complex of two rodent species

The distribution of immunoreactivity to calbindin, calretinin, and parvalbumin in the vestibular nuclear complex and the adjacent nucleus prepositus hypoglossi was studied in rats and gerbils. The distribution of stained fibers was the same for both rodent species. All three calcium-binding proteins were present in vestibular afferents. However, none of the three proteins were present in all afferent fibers. Many fibers were labeled in the vestibular nerve and in fascicles of the descending vestibular nucleus, as well as ascending fibers in the superior vestibular nucleus and fibers directed to the medial vestibular nucleus. Labeled terminals were present in the medial vestibular nucleus, especially along the ventricular border, in the neuropil of the superior vestibular nucleus, and scattered in the descending and ventral portions of the lateral vestibular nucleus. Calbindin- and parvalbumin-positive terminals, but not calretinin-positive terminals, were present in the neuropil of the dorsal lateral vestibular nucleus, especially surrounding the large neuronal somas. Some of these terminals are presumably from cerebellar Purkinje cells, which were also labeled by both antibodies. The pattern of parvalbumin immunoreactivity was slightly different from that of calbindin, indicating that parvalbumin might be contained in additional fibers. Some neurons in the vestibular nuclear complex were labeled with antibodies to calretinin, but few cells were stained with either calbindin or parvalbumin antibodies. The largest group of calretinin-positive cells was a cluster of small- to medium-sized neurons located in a densely stained mesh of dendrites and terminals in the medial vestibular nucleus, adjacent to the ventricular border. © 1996 Wiley-Liss, Inc.     

Distribution of choline acetyltransferase and acetylcholinesterase in vocal control nuclei of the budgerigar (Melopsittacus undulatus)

The present study used histochemical methods to map the distributions of choline acetyl transferase (ChAT) and acetylcholinesterase (AChE) in the vocal control nuclei of a psittacine, the budgerigar (Melopsittacus undulatus). The distributions of ChAT and AChE in budgerigars appeared similar to that in oscine songbirds despite evidence that these systems have evolved independently. The magnicellular nucleus of the lobus parolfactorius in budgerigars, like the area X in songbirds, contained many ChAT labeled somata, fibers, and varicosities and stained densely for AChE. In contrast, the robust nucleus of the archistriatum (RA) and the supralaminar area of the frontal neostriatum in budgerigars, like the RA and the magnicellular nucleus of the neostriatum (MAN) in songbirds, respectively, contained few or no ChAT labeled somata, fibers, and varicosities and stained lightly for AChE. The central nucleus of the lateral neostriatum in budgerigars, like the higher vocal center (HVC) in songbirds, contained no ChAT labeled somata, moderate densities of ChAT labeled fibers and varicosities, and moderate levels of AChE staining. Two nuclei, the oval nucleus of the hyperstriatum ventrale (HVo) and the oval nucleus of the anterior neostriatum (NAo), contained no ChAT labeled somata, dense ChAT labeled fibers and varicosities, and moderate to high levels of AChE staining. The HVo and the NAo have no counterparts in songbirds but may be important vocal control nuclei in the budgerigar. Cholinergic enzymes are also described in other regions which may be involved in budgerigar vocal behavior, including the basal forebrain, the torus semicircularis, and the hypoglossal nuclei (nXII). © 1996 Wiley-Liss, Inc.     

A cholinergic projection to the rat superior colliculus demonstrated by retrograde transport of horseradish peroxidase and choline acetyltransferase immunohistochemistry

Acetylcholinesterase (AChE) has been localized by histochemistry in the superior colliculus and in the tegmentum of the caudal midbrain and rostral pons of the rat. The pattern of AChE localization in the superior colliculus was characterized by homogeneous staining in the superficial layers and patchlike staining in the intermediate gray layer. In the tegmentum, AChE was localized in the pedunculopontine nucleus (PPN), beginning rostrally at the caudal pole of the substantia nigra and extending caudally to the level of the parabrachial nuclei, and in the lateral dorsal tegmental nucleus (LDTN) of the central gray. The localization of AChE in these nuclei overlapped the distribution of neurons stained by immunohistochemistry using an antibody to choline acetyltransferase (ChAT), the synthesizing enzyme of the neurotransmitter acetylcholine. Other neighboring areas that were stained with AChE, but that did not contain ChAT-immunoreactive neurons, included the microcellular tegmental nucleus and the ventral tegmental nucleus. Neurons in the PPN and LDTN were determined to be potential sources of the cholinergic projection to the intermediate gray layer of the rat superior colliculus by double labelling with retrograde transport of horseradish peroxidase (HRP) combined with the immunohistochemical localization of ChAT. Three populations of neurons were identified. A predominantly ipsilateral ChAT-immunoreactive population was located in the pars compacta subdivision of PPN (PPNpc). Retrograde HRP-labelled neurons in the pars dissipata subdivision of the PPN (PPNpd), located ventral to the superior cerebellar peduncle (SCP) at the level of the inferior colliculus, composed a second population that was predominantly contralateral but was not ChAT immunoreactive. A third population of retrogradely labelled neurons was predominantly ipsilateral and ChAT immunoreactive and was located in the LDTN. These findings compared favorably with the full extent of the projection from this tegmental region revealed by retrograde transport of HRP from the superior colliculus when more compatible fixation and chromogen procedures were used. The results suggest that the PPN and the LDTN are two sources of the cholinergic input to the superior colliculus. Since the PPN also has extensive efferent, and afferent, connections with basal-ganglia-related structures, this cholinergic excitatory input to the superior colliculus, like the GABA-ergic inhibitory input from the substantia nigra pars reticulata, may provide the basis for an additional influence of the basal ganglia on visuomotor behavior.     

Distribution of reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) cells and fibers in the monkey amygdaloid complex.

The NADPH-d histochemical method stains a selective population of neurons in the central nervous system. Although the functional significance of the enzyme in these cells is unknown, it has nonetheless proved to be a useful marker. In the present study we describe the distribution of NADPH-d-positive cells and fibers in the amygdaloid complex of the Macaca fascicularis monkey. NADPH-d-positive neurons were distributed throughout the amygdaloid complex. Based on the intensity of the reaction product, three different types of NADPH-d-positive cells were described: type 1 cells, the most intensely stained, varied in morphology and were most commonly found in the accessory basal, basal, and lateral nuclei and in the nucleus of the lateral olfactory tract; type 2 cells, the most common NADPH-d-positive cells, were more lightly stained, were generally stellate in shape, and were found in the lateral, basal, and accessory basal nuclei; type 3 cells were very lightly stained, oval or round in shape, and mostly found in the medial, anterior cortical, and paralaminar nuclei. NADPH-d staining was also associated with axonal fiber plexuses in various regions of the amygdala. The highest densities of stained fibers were found in the lateral nucleus, the parvicellular portion of the accessory basal nucleus, and the anterior amygdaloid area. The lowest densities of NADPH-d-positive fiber staining were found in the amygdalohippocampal area, in the lateral part of the central nucleus, and in the intercalated nuclei. In addition to the neuronal and fiber staining, a diffuse, blue neuropil staining was also observed, most commonly in the anterior cortical nucleus, the medial nucleus, the intercalated nuclei, and especially in the amygdalohippocampal area. The distribution of NADPH-d staining often respected nuclear boundaries within the amygdala and was particularly helpful in clarifying the borders of the amygdalohippocampal area.     

Distribution of choline acetyltransferase immunoreactive axons and terminals in the rat and ferret brainstem.

A survey was made of the density of the cholinergic innervation of different parts of the brainstem of the rat and ferret. Sections of rat and ferret brainstems were stained for choline acetyltransferase (ChAT) immunoreactivity by using a sensitive immunocytochemical method. Adjacent sections were stained for acetylcholinesterase activity or Nissl substance. The density of the distribution of fine calibre, varicose ChAT-positive axons, assumed to represent cholinergic terminals, was categorised arbitrarily into high, medium, or low. A high density of ChAT-positive terminals was found in all or parts of these structures: interpeduncular nucleus, superficial grey layer of the superior colliculus (ferret), intermediate layers of the superior colliculus, lateral part of the central grey (rat), an area medial to the parabigeminal nucleus (rat), pontine nuclei, ventral tegmental nucleus (rat), midline pontine reticular formation, and an area ventral to the exit point of the 5th nerve (ferret). A medium density of ChAT-positive terminals was observed in all or parts of: the substantia nigra zona compacta (ferret), ventral tegmental area (ferret), superficial grey layer of the superior colliculus, intermediate and deep layers of the superior colliculus, lateral central grey, area medial to the parabigeminal nucleus, inferior colliculus, dorsal tegmental nucleus, ventral tegmental nucleus (ferret), pontine nuclei, ventral nucleus of the lateral lemniscus (ferret), midline pontine reticular formation, ventral cochlear nucleus, dorsal cochlear nucleus, lateral superior olive, spinal trigeminal nuclei, prepositus hypoglossal nucleus, lateral reticular nucleus, paragigantocellular nucleus, and the dorsal column nuclei including the cuneate, external cuneate, and gracile nuclei. A low density of ChAT-positive terminals was seen throughout the remainder of the brainstem of the rat and ferret, but these terminals were absent from the medial superior olive, substantia nigra zona reticulata (rat), and the central part of the ferret lateral superior olive. A pericellular-like distribution of ChAT-positive terminals was observed in the ventral cochlear nucleus and in association with some of the cells of the nucleus of the mesencephalic tract of the trigeminal nerve. A climbing fibre type arrangement of ChAT-positive terminals was found in the substantia nigra zona compacta (ferret) and medial reticular formation. In general, the distribution of staining for AChE activity reflected that of the distribution of ChAT immunoreactivity in the brainstem, except in a few regions where there were also species differences in the distribution of ChAT-positive terminals, e.g., in the superficial grey layer of the superior colliculus and in the substantia nigra.(ABSTRACT TRUNCATED AT 400 WORDS)     

A comparison of the subnuclear and ultrastructural distribution of acetylcholinesterase and choline acetyltransferase in the rat interpeduncular nucleus

The subnuclear and synaptic staining patterns for acetylcholinesterase (AChE) activity and choline acetyltransferase (ChAT) activity were studied in the rat interpeduncular nucleus (IPN) using histochemical and immunohistochemical methods. AChE reactivity was prominent in the neuropil of the rostral, lateral and dorsomedial subnuclei, whereas ChAT immunoreactivity was confined to axons and terminals in the rostral, intermediate and central subnuclei. AChE-positive somata were evident in all the subnuclear divisions of the IPN, and possessed reaction product in the rough endoplasmic reticulum and nuclear envelope. ChAT-positive somata were not present in the IPN. Characteristic axodendritic synapses in the rostral, intermediate and central subnuclei possessed ChAT immunoreactivity presynaptically, and AChE reactivity both pre- and postsynaptically. Other synaptic arrangements in the lateral subnucleus lacked ChAT-immunoreactive terminals, yet possessed prominent AChE reactivity. The results of the present study reveal that AChE reactivity and ChAT immunoreactivity are heterogeneously distributed among the subnuclear divisions of the rat IPN, and that AChE reactivity is present in both the cholinoceptive and noncholinoceptive subnuclei. Although neuronal colocalization of ChAT and AChE activity is not evident in the IPN, AChE-positive neurons are in receipt of putative cholinergic, as well as peptidergic, afferent inputs.     

A comparison of the distribution of central cholinergic neurons as demonstrated by acetylcholinesterase pharmacohistochemistry and choline acetyltransferase immunohistochemistry

The topographical distribution of cholinergic cell bodies has been studied in the rat brain and spinal cord by choline acetyltransferase (ChAT)-immunohistochemistry and acetylcholinesterase (AChE)-pharmacohistochemistry using diisopropylfluorophosphate (DFP). The ChAT-containing cells and the cells that stained intensely for AChE 4-8 hr after DFP were mapped in detail on an atlas of the forebrain (telencephalon, diencephalon) hindbrain (mesencephalon, rhombencephalon) and cervical cord (C2, C6). Striking similarities were observed between ChAT-positive cells and neuronal soma that stained intensely for AChE both in terms of cytoarchitectural characteristics, and with respect to the distribution of the labelled cells in many areas of the central nervous system (CNS). In the forebrain these areas include the caudatoputamen, nucleus accumbens, medial septum, nucleus of the diagonal band, magnocellular preoptic nucleus and nucleus basalis magnocellularis. In contrast, a marked discrepancy was observed in the hypothalamus and ventral thalamus where there were many neurons that stained intensely for AChE, but where there was an absence of ChAT-positive cells. No cholinergic perikarya were detected in the cerebral cortex, hippocampus, amygdala and dorsal diencephalon by either histochemical procedure. In the hindbrain, all the motoneurons constituting the well-established cranial nerve nuclei (III-VII, IX-XII) contained ChAT and exhibited intense staining for AChE. Further, a close correspondence was observed in the distribution of labeled neurons obtained by the two histochemical procedures in the midbrain and pontine tegmentum, including the laterodorsal tegmental nucleus, some areas in the caudal pontine and bulbar reticular formation, and the central gray of the closed medulla oblongata. On the other hand, AChE-intense cells were found in the nucleus raphe magnus, ventral part of gigantocellular reticular nucleus, and flocculus of the cerebellum, where ChAT-positive cells were rarely observed. According to both techniques, no positive cells were seen in the cerebellar nuclei, the pontine nuclei, or the nucleus reticularis tegmenti pontis. Large ventral horn motoneurons and, occasionally, cells in the intermediomedial zone of the cervical cord displayed ChAT-immunoreactivity and intense AChE staining. On the other hand, AChE-intense cells were detected in the dorsal portion of the lateral funiculus, but immunoreactive cells were not found in any portion of the spinal cord white matter.(ABSTRACT TRUNCATED AT 400 WORDS)     

Distribution of calbindin-D28k immunoreactivity in the monkey temporal lobe: The amygdaloid complex

Calbindin-D_28k is a calcium-binding protein located in a variety of neuronal cell types in many regions of the central nervous system. In the present study, we describe the distribution of calbindin-D_28k-immunoreactive cells, fibers, and terminals in the monkey amygdaloid complex. Calbindin-D_28k-immunoreactive neurons could be divided into four major cell types. Neurons of the first three cell types demonstrated clearly stained dendrites that were either aspiny or had a few spines on their distal portions. Type 1 cells were small, stellate, or multipolar and found throughout the amygdala. Type 2 cells were large, multipolar and were most commonly found in the deep nuclei, particularly in the lateral nucleus, intermediate division of the basal nucleus, accessory basal nucleus and in the periamygdaloid cortex. Type 3 cells were fusiform, of various sizes, and were found throughout the amygdala. Type 4 cells were quite large and lightly stained; the dendrites of these cells were usually unstained. The size, shape, and location of Type 4 labeled cell bodies suggested that they might be the large, modified pyramidal cells that constitute the projection neurons of the amygdala. Type 4 cells were observed primarily in the lateral, basal, and accessory basal nuclei and in the periamygdaloid cortex. Calbindin-D_28k-immunoreactive fibers and terminals were difficult to observe in the amygdala partly because of a diffuse, finely granular neuropil labeling that was particularly dense in the anterior cortical and medial nuclei, in the central nucleus, and in the periamygdaloid cortex. The neuropil labeling was substantially lighter in the lateral, basal, and accessory basal nuclei. Conspicuous linear profiles resembling the “calbindin bundles” of the neocortex were evident in large numbers in the accessory basal nucleus, the medial portion of the parvicellular division of the basal nucleus, in the amygdalohippocampal area, and in the periamygdaloid cortex. There were calbindin-D_28k-positive fibers in the stria terminalis and in the ventral amygdalofugal pathway. When the distributions of calbindin-D_28k and parvalbumin immunoreactivity in the monkey amygdaloid complex were compared, it appeared that the overall distribution of these two calcium-binding proteins was generally complementary rather than overlapping. © 1993 Wiley-Liss, Inc.     

Distribution of serotonin transporter labeled fibers in amygdaloid subregions: implications for mood disorders.

BACKGROUND: The serotonin transporter 5-HTT mediates responses to serotonin reuptake inhibitors (SSRIs), a mainstay treatment in mood disorders. The amygdala, a key emotional processing center, has functional abnormalities in mood disorders, which resolve following successful SSRI treatment. To better understand the effects of SSRIs in mood disorders, we examined the distribution of 5-HTT labeled fibers relative to specific nuclear groups in the amygdala. METHODS: Immunocytochemical techniques were used to chart 5-HTT labeled fibers in the amygdala in coronal sections through the brain of six adult Macaques. Nissl staining was used to define nuclear groups in the amygdala. RESULTS: The serotonin transporter 5-HTT is distributed heterogeneously in the primate amygdala, with the lateral subdivision of the central nucleus, intercalated cell islands, amygdalohippocampal area, and the paralaminar nucleus showing the heaviest concentrations. CONCLUSIONS: 5HTT-labeled fibers are very densely concentrated in output regions of the amygdala. High concentrations of 5-HTT-positive fibers in the central nucleus indicate that tight regulation of serotonin is critical in modulating fear responses mediated by this nucleus. High concentrations of 5-HTT-labeled fibers in the intercalated islands and parvicellular basal nucleus/paralaminar nucleus, which contain immature -appearing neurons, suggest a potential trophic role for serotonin in these subregions.     

Compartmental ordering of cholinergic innervation in the mediodorsal nucleus of the thalamus in human brain

The cholinergic innervation of the mediodorsal (MD) nucleus of the thalamus was visualized immunohistochemically in human brain postmortem, using an antibody against human choline acetyltransferase (ChAT). The ChAT staining of the MD nucleus was more intense than in the surrounding thalamic nuclei but weaker than that of the striatum. No ChAT-positive cell bodies were detected. The ChAT-positive neuropil was unevenly distributed, with patches of dense immunoreactivity contrasting with a weaker surrounding matrix. In adjoining sections stained for ChAT immunoreactivity and for acetylcholinesterase (AChE) activity, the zones enriched in ChAT-immunostained neuropil corresponded to AChE-rich regions. The three-dimensional reconstruction of the richest zone in AChE/ChAT activity evidenced a cylindrical organization throughout the rostrocaudal axis of the MD nucleus. Counts of ChAT-positive varicosities confirmed an inhomogeneous distribution; the density of varicosities was 30% higher in ChAT-rich regions than in surrounding matrix. These findings suggest that the activity of intrinsic neurons within the nucleus may be differentially regulated by cholinergic systems.     

Cholinergic and monoaminergic innervation of the cat's thalamus: comparison of the lateral geniculate nucleus with other principal sensory nuclei

The cholinergic and monoaminergic innervation of the lateral geniculate nucleus (GL) and other thalamic nuclei in the cat was examined by using immunocytochemical and tract-tracing techniques. Cholinergic fibers, identified with an antibody to choline acetyltransferase (ChAT), are present in all layers of the GL. They are fine in caliber and exhibit numerous swellings along their lengths. The A layers, the magnocellular C layer, and the medial interlaminar nucleus are rich in cholinergic fibers that give rise to prominent clusters of boutons, while the parvicellular C layers contain fewer fibers that are more uniformly distributed. The interlaminar zones are largely devoid of ChAT-immunoreactive fibers. Double-label experiments show that cholinergic projections to the GL originate from two sources, the pedunculopontine reticular formation (PPT) and the parabigeminal nucleus (Pbg). The PPT contributes cholinergic fibers to all layers, while Pbg projections are limited to the parvicellular C layers. The lateral geniculate nucleus has a much greater density of cholinergic fibers than the other principal sensory nuclei: the density of fibers in the A layers is more than three times greater than that in the ventral posterior nucleus (VP) or the ventral division of the medial geniculate nucleus (GMv). In contrast, serotonin (5-HT)-immunoreactive fibers are distributed with equal density across the principal thalamic nuclei, while tyrosine hydroxylase (TH)-immunoreactive fibers (presumed to contain norepinephrine) are noticeably less dense in the GL than in the others. Monoaminergic fibers also differ from cholinergic fibers in their laminar distribution within the GL: both TH- and 5HT-immunoreactive fibers are distributed evenly across the layers and interlaminar zones and are slightly more abundant in the parvicellular C layers than in the other layers. Other thalamic nuclei rich in cholinergic fibers include the pulvinar nucleus, the ventral lateral geniculate nucleus, the intermediate nucleus of the lateral group, the lateral medial and suprageniculate nuclei (Graybiel and Berson: Neuroscience 5:1175-1238, '80), and the paracentral and central-lateral components of the intralaminar nuclei. This pattern matches the distribution of projections from the PPT and is similar, but not identical, to the pattern of acetylcholinesterase staining. The fact that most of the nuclei rich in cholinergic fibers have been implicated in visual sensory or visual motor functions suggests that cholinergic projections from the reticular formation play an especially important role in visually guided behavior.     

Distribution of demyelinating lesions in pontine and extrapontine myelinolysis — Three autopsy cases including one case devoid of central pontine myelinolysis

Summary The location of the neuropeptides methionine-enkephalin (ME), neurotensin (NT), neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) within the amygdaloid complex of healthy human individuals, schizophrenics and patients suffering from Huntington's chorea was studied qualitatively by means of immunohistochemistry. VIP-like immunoreactivity (IR) was present predominantly in a dense cluster of fibers and terminals in the central amygdaloid nucleus. ME-IR was observed in fibers, terminals and cell bodies in the same subnucleus, exhibiting a characteristical distribution pattern. NT-positive cell bodies were situated within the center of the central amygdaloid nucleus, fibers and terminals being encountered mainly at the periphery. NPY-IR was found to be evenly distributed throughout the amygdala. Distribution and staining intensity of ME, NPY and NT in the amygdala showed no qualitatively recognizable difference between the normal and schizophrenic specimens, whereas VIP-IR appeared to be slightly increased in the central amygdaloid nucleus of schizophrenics. In the choreic cases, the considerably shrunken amygdala exhibited only very low staining intensity of the four investigated neuropeptides.     

Distribution of neurotensin immunoreactivity within the human amygdaloid complex: a comparison with acetylcholinesterase- and Nissl-stained tissue sections.

In a previous study, we reported marked depletion of neurotensin-immunoreactivity (NT-IR) within selected regions of the amygdala of patients with Alzheimer's disease. The significance of these observations was partly obscured largely because we lacked a thorough understanding of the innervation pattern of neurotensin in the normal human amygdala. Accordingly, in the present study, we used a polyclonal antibody against neurotensin to characterize the distribution and morphology of neurotensin-immunoreactive neuronal elements within the human amygdaloid complex. NT-IR occurred in a topographic manner that respected the cytoarchitectural boundaries of the amygdaloid subregions as defined by Nissl staining and acetylcholinesterase histochemistry. Most NT-IR in the amygdala was contained within beaded fibers and dot-like puncta. Within the subnuclei of the amygdala, immunoreactive neuritic elements were most dense within the central nucleus followed by the medial nucleus and intercalated nuclei. The anterior amygdaloid area, basal complex, paralaminar nucleus, cortical nucleus, cortical-amygdaloid transition area, and amygdalohippocampal area contained moderate densities of immunoreactivity. The accessory basal and lateral nuclei exhibited scant NT-IR. Immunoreactive neurons were found only within the anterior amygdaloid area and the central, medial, intercalated, and lateral capsular nuclei. The distribution of NT-immunoreactive processes and cell bodies within selected regions of the amygdala provides an anatomical substrate that may explain, in part, the neuromodulatory actions of neurotensin upon autonomic, endocrine, and memory systems.     

Distribution of dopaminergic fibers in the central division of the extended amygdala of the rat

The distribution of dopaminergic fibers in the principal components of the central extended amygdala (central amygdaloid nucleus (Ce), substantia innominata, and bed nucleus of the stria terminals (BNST)), was studied using immunocytochemistry against tyrosine hydroxylase, dopamine β-hydroxylase and dopamine. Dopamine fibers were found most densely distributed in the dorsolateral subdivision of the BNST and the lateral part of the Ce. Smaller numbers of dopaminergic fibers were found in the rest of the central extended amygdala. In contrast, dopamine β-hydroxylase fibers were virtually absent from the dorsolateral bed nucleus of the stria terminalis and lateral part of the central amygdaloid nucleus, but were distributed in a moderate density in the medial part of Ce, dorsal substantia innominata and posterolateral BNST. Our results show that dopamine fibers are most concentrated over those regions of the central extended amygdala with large numbers of GABAergic neurons whose projections remain within the central extended amygdala, while noradrenergic fibers are most heavily concentrated over those regions containing a large proportion of brainstem projection neurons. That dopamine fibers are concentrated over regions with GABAergic medium spiny neurons suggests that those regions might be organized as a striatal parallel.     

Immunohistochemical localization of substance P and enkephalin in the nucleus tractus solitarii of the rhesus monkey, Macaca mulatta

The nucleus tractus solitarii in the monkey Macaca mulatta was found to have several subdivisions based upon cytoarchitectonics and immunohistochemistry. Subdivisions that could be identified included commissural, medial, parvicellular, dorsolateral, ventrolateral, intermediate, and interstitial. Substance P and enkephalin immunoreactivity was localized within discrete regions of the nucleus tractus solitarii, by means of the peroxidase-antiperoxidase technique. Substance P immunoreactivity occurred most frequently in the interstitial subdivision of the nucleus tractus solitarii. Moderate accumulations of substance P immunoreactivity were present in the commissural, medial, parvicellular, dorsolateral, and intermediate subdivisions, but very little was present in the ventrolateral subdivision. Enkephalin immunoreactivity followed the staining patterns of substance P; however, the amounts of enkephalin immunoreactivity were less than amounts for substance P. Following colchicine treatment, large numbers of enkephalin-immunoreactive neurons were distributed throughout all subdivisions, many being located in the parvicellular and medial subdivisions. The few substance P-immunoreactive neurons found were restricted to the parvicellular subdivision. The distribution of substance P and enkephalin immunoreactivity in M. mulatta is very similar to that described in the cat and rat. In addition, the extensive overlap of the distribution of these two putative neurotransmitters provides morphological evidence for their possible participation in the autonomic regulation within the nucleus tractus solitarii.     

Immunohistochemical localization of gamma-aminobutyric acid- and aspartate-containing neurons in the guinea pig vestibular nuclei

The immunohistochemical distributions of gamma-aminobutyric acid (GABA)- and aspartate-containing neurons were studied in the guinea pig vestibular nuclei using purified antisera to GABA and aspartate, respectively. Most GABA-containing neurons had small cell bodies and were scattered throughout all regions of the vestibular nuclei. The largest number of these cells was found in the medial nucleus. Intraventricular injection of colchicine markedly increased GABA-like immunoreactivity in these cell bodies. GABA-containing terminals were distributed throughout all 4 subdivisions of the nuclei, with the richest localization found around the floor of the fourth ventricle. Various sized aspartate-containing neurons were noted in the vestibular nuclei and small cells were present in the superior, medial and lateral nucleus. Medium-sized cells were observed throughout the vestibular nuclei. Giant cells in the lateral nucleus also contained aspartate and were surrounded by GABA-like immunoreactive terminals, thereby suggesting the modulation of aspartate-containing neurons by GABAergic fibers from Purkinje cells.