Amygdalohippocampal Area Research Articles

Expression and glucocorticoid regulation of natriuretic peptide clearance receptor (NPR-C) mRNA in rat brain and choroid plexus

The natriuretic peptide clearance receptor (NPR-C) binds atrial natriuretic peptide, brain natriuretic peptide and C-type natriuretic peptide with high affinity. This receptor lacks an intracellular guanylate cyclase domain, and is believed to exert biological actions by sequestration of released natriuretic peptides and/or inhibition of adenylate cyclase. The present report summarizes the first detailed mapping of NPR-C mRNA in rat brain. In situ hybridization analysis revealed high levels of NPR-C mRNA expression in frontal and retrosplenial granular cortices, medial preoptic nucleus, ventral cochlear nucleus and choroid plexus. NPR-C mRNA expression was also observed in deep layers of neocortex and limbic cortex, posterior cortical amygdala, ventral subiculum, amygdalohippocampal area, and dentate gyrus. Positive hybridization signal was observed in both anterior and intermediate lobes of the pituitary gland. Regulatory studies indicated that expression of NPR-C mRNA was increased in the medial preoptic nucleus of adrenalectomized rats, suggesting negative glucocorticoid regulation. No changes in NPR-C mRNA expression were observed in frontal cortex or choroid plexus. These results suggest a role for the NPR-C in modulation of natriuretic peptide availability and/or adenylate cyclase activity in a subset of central natriuretic peptide circuits concerned with cortical, olfactory and neuroendocrine functions. Response of the NPR-C gene to changes in circulating hormones suggests the capacity for glucocorticoid modulation of natriuretic peptide action at the receptor level.

Calbindin-D28k-immunoreactive cells and fibres in the human amygdaloid complex

The distribution of calbindin-D28k-immunoreactive cells and fibres in five human amygdalae was analysed from sections that had been stained immunohistochemically with a monoclonal antibody raised against calbindin-D28k. The highest density of calbindin-D28k-positive neurons were found in the anterior cortical, medial, posterior cortical and accessory basal nuclei, in the parvicellular division of the basal nucleus and in the amygdalohippocampal area. The lowest densities of immunopositive neurons were found in the paralaminar nucleus, in the periamygdaloid cortex (PAC1 and PACo) and in some of the intercalated nuclei. The deep nuclei (lateral, basal and accessory basal nuclei) contained a high density of calbindin-D28k-immunoreactive fibres and terminals. The cortical nuclei and the central nucleus were characterized by intense neuropil labelling. Morphologically, a large majority of the calbindin-D28k-immunoreactive neurons were aspiny or sparsely spiny and resembled inhibitory local circuit neurons. A small population of lightly-stained, pyramidal-shaped neurons was also observed. In most of the amygdaloid nuclei, calbindin-D28k-immunoreactive fibres travelled close to each other and formed bundles, which suggests that some of the immunostained neurons were double-bouquet cells. In the paralaminar nucleus, the calbindin-D28k-immunoreactive axons formed tortuous plexus (100–200mm in diameter) that surrounded several unstained somata.This study provides baseline information on the morphology and distribution of calcium-binding protein-containing inhibitory cells and fibres immunoreactive for calbindin-D28k in the human amygdaloid complex. This information can be used in future studies on the pathogenesis of diseases known to damage the amygdala, such as Alzheimer's disease and temporal lobe epilepsy.

Calretinin-immunoreactive cells and fibers in the human amygdaloid complex.

Calretinin is a calcium-binding protein that colocalizes with GABA in the cerebral cortex and hippocampus of the rat and the monkey. In the present study, we investigated the distribution of calretinin-immunoreactive cells and fibers in the human amygdaloid complex. A conspicuous feature was the high density of calretinin neurons in the human amygdala. The highest densities of the calretinin-immunoreactive neurons were observed in the anterior cortical nucleus, accessory basal nucleus, amygdalohippocampal area, and in the nucleus of the lateral olfactory tract. The paralaminar nucleus, central nucleus, medial nucleus, and the periamygdaloid cortex contained the lowest densities of calretinin neurons. In most of the amygdaloid areas, the calretinin cells had the appearance of aspiny or sparsely spiny local circuit neurons. However, in the amygdalohippocampal area, we found also densely spined dendrites. The cortical areas and the central nucleus were characterized by intense neuropil labeling, while the deep nuclei contained a high density of calretinin-immunoreactive fibers and terminals. Calretinin immunoreactivity was also found in the intra-amygdaloid fiber bundles, stria terminalis, and in the ventral amygdalofugal pathway. This suggests that in addition to the local circuit neurons, calretinin immunoreactivity is also located in neurons that connect the amygdaloid complex with the other brain areas. The distribution and morphological characteristics of calretinin-immunoreactive neurons differed from those of another calcium-binding protein, parvalbumin, in the human amygdala (Sorvari et al. [1995] J. Comp. Neurol. 360:185-212). This suggests that these two calcium-binding proteins are located in different populations of neurons.

Temporal lobe lesion-induced obesity in rats: An anatomical investigation of the posterior amygdala and hippocampal formation

Bilateral lesions centered in the posterodorsal amygdala of female rats resulted in hyperphagia and excessive weight gain (mean = 65.3 g in 20 days compared to 6.8 g for control animals). The brain damage always extended posteriorly into the ventral hippocampal formation. However, lesions that were confined to the ventral hippocampus or amygdalohippocampal area had no effect on daily food intake or body weight, nor did lesions at any other hippocampal site. In a previous study, lesions of the basolateral, corticomedial, and anterior groups of amygdaloid nuclei failed to affect food intake or body weight. It is concluded that the posterodorsal aspect of the amygdala is the critical site for this experimentally induced obesity syndrome. New coordinates for the effective site are presented.

Expression of activin receptors type I and II only partially overlaps in the nervous system

In situ hybridization was used to localize mRNA encoding two cooperative serine/threonine kinase receptors. Activin receptor IIA mRNA in the adult rat brain is highly expressed in the dentate gyrus, in the pyramidal neurones of CA3 and CA1, in the entorhinal cortex, in the cortical amygdaloid nucleus and in the amygdalohippocampal area. In the E16 rat embryo, labelling was found in the dorsal root ganglion neurones and in the spinal cord. Activin type I receptor (ALK-2/R-1) labelling was also localized to the hippocampal formation but with an even distribution over the granular cells of the dentate gyrus, the CA3 and CA1 pyramidal neurones, while no labelling was found in the entorhinal or amygdaloid areas. In the E16 rat no neuronal labelling was found. The incomplete overlap of these two expression patterns suggests that these receptors may locally have other partners for forming signalling receptor complexes.

Intrinsic connections of the rat amygdaloid complex: projections originating in the basal nucleus.

The amygdaloid complex is involved in associational processes, such as the formation of emotional memories about sensory stimuli. However, the anatomical connections through which the different amygdaloid nuclei process incoming information and communicate with the other amygdaloid nuclei, is poorly understood. As part of an ongoing project aimed at elucidating the intrinsic connections of the rat amygdaloid complex, we injected the anterograde tracer PHA-L (Phaseolus vulgaris-leucoagglutinin) into different rostrocaudal levels of the basal nucleus of the amygdala in 21 rats and analyzed the distribution of labeled fibers and terminals throughout the amygdaloid complex. The connectional analysis, together with cytoarchitectonic observations, suggested that contrary to previous notions the basal nucleus in the rat has three divisions: magnocellular, intermediate, and parvicellular. The magnocellular division has heavy reciprocal connections with the lateral portion of the parvicellular division and the intermediate division projects weakly to the parvicellular division, whereas the projection from the medial portion of the parvicellular division to the intermediate division is heavy and the lateral and medial portions of the parvicellular division are only weakly interconnected, as are the magnocellular and intermediate divisions. The main intraamygdaloid targets of the basal nucleus projections are the nucleus of the lateral olfactory tract, the anterior amygdaloid area, the medial and capsular divisions of the central nucleus, the anterior cortical nucleus, and the amygdalohippocampal area. Our findings provide the most detailed understanding of the intra-amygdala connections of the basal nucleus to date and show that the connections within the basal nucleus and between the basal nucleus and other amygdaloid areas are more widespread and topographically organized than previously recognized.

Distribution of parvalbumin‐immunoreactive cells and fibers in the human amygdaloid complex

The calcium-binding protein, parvalbumin, was localized immunohistochemically in the human amygdaloid complex. Neuronal cell bodies and fibers that are immunoreactive to parvalbumin were observed in most of the amygdaloid nuclei and cortical areas. Three types of immunoreactive aspiny neurons, ranging from small spherical cells (type 1) to large multipolar cells (type 2) and fusiform cells (type 3), were observed. The densities of the types of neurons that were parvalbumin-immunoreactive varied in the different regions of the amygdala. The highest densities of parvalbumin-immunoreactive neurons were observed in the lateral nucleus, in the magnocellular and intermediate divisions of the basal nucleus, in the magnocellular division of the accessory basal nucleus and in the amygdalohippocampal area. The regions containing the lowest density of parvalbumin-immunoreactive cells were the paralaminar nucleus, the parvicellular division of the basal nucleus, the central nucleus, the medial nucleus and the anterior cortical nucleus. In general, the distribution of immunoreactive fibers and terminals paralleled that of immunoreactive cells. Parvalbumin-immunoreactive varicose fibers formed basket-like plexi and cartridges around the unstained neurons, which suggests that parvalbumin is located in GABAergic basket cells and chandelier cells, respectively. The distribution of parvalbumin-immunoreactive profiles in the human amygdaloid complex was similar to, rather than different from that previously reported in the monkey amygdala (Pitkänen and Amaral [1993] J. Comp. Neurol. 331:14-36). This study provides baseline information about the organization of GABAergic inhibitory circuitries in the human amygdaloid complex.

Intrinsic connections of the rat amygdaloid complex: Projections originating in the lateral nucleus

The amygdaloid complex receives sensory information from a variety of sources. A widely held view is that the amygdaloid complex utilizes this information to orchestrate appropriate species-specific behaviors to ongoing experiences. Relatively little is known, however, about the circuitry through which information is processed within the amygdaloid complex. The lateral nucleus is the major recipient of extrinsic sensory information and is the origin of many intra-amygdaloid projections. In this study, we reinvestigated the organization of intra-amygdaloid projections originating from the lateral nucleus using the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L). The lateral nucleus has highly organized intranuclear connections. Dense projections interconnect rostral and caudal levels of the lateral and the medial divisions of the nucleus, and the lateral and medial divisions of the lateral nucleus are also interconnected. The major extranuclear projections of the lateral nucleus are (in descending order of magnitude) to the accessory basal nucleus, the basal nucleus, the periamygdaloid cortex, the dorsal portion of the central division of the medial nucleus, the posterior cortical nucleus, the capsular division of the central nucleus, and the lateral division of the amygdalohippocampal area. The pattern of extranuclear projections varied depending on the rostrocaudal or mediolateral location of the injection site within the lateral nucleus. These findings indicate that intra-amygdaloid projections originating in the lateral nucleus are both more widespread and more topographically organized than was previously appreciated.

Distribution of neurons of origin of zinc-containing projections in the amygdala of the rat

The present study describes the distribution of neurons of origin of zinc-containing pathways in the amygdaloid complex of the rat, using the selenium method for simultaneous retrograde labeling of all zinc-containing neurons. With this method, vesicular ionic zinc is precipitated intravitally with selenium compounds and transported retrogradely to the parent neurons, where it can be visualized by silver amplification. Neurons labeled retrogradely with silver-amplified precipitate were observed in all amygdaloid nuclei except for the lateral olfactory tract nucleus, the accessory olfactory tract nucleus and the central nucleus. Very few labeled cell bodies were seen in the anterior amygdaloid area and the medial nucleus. The amygdalo-hippocampal area and the amygdalo-piriform transition area both showed a substantial number of labeled somata throughout their rostrocaudal extent. In the anterior cortical nucleus, very few labeled cell bodies were found in the rostral pole, whereas they were abundant in the caudal quarter of the nucleus. In the posterolateral cortical nucleus, the number of labeled cell bodies increased gradually; there were none in the rostral pole, but most of the neurons in the caudal part were labeled. The posteromedial cortical nucleus contained a great number of labeled somata, but with some variation in the rostrocaudal extent of the nucleus. Considerable numbers of labeled neurons were observed throughout the lateral nucleus. In the basolateral nucleus, a small number of labeled cell bodies was present in the rostral half, but a gradual increase was observed in the caudal direction. Finally, in the basomedial nucleus, very few labeled cell bodies were present in the rostral two-thirds, whilst a considerable number was encountered in the caudal one-third. Possible functional implications of neuronal zinc are considered. The distribution of neurons of origin of zinc-containing projections has been compared with previously described intrinsic connections of the rat amygdala, and tracts that may possibly be zinc-containing are outlined and discussed. It is concluded that in all probability a substantial proportion of the intrinsic connectivity of the rat amygdaloid complex is zinc-containing.

Afferent connections of the medial frontal cortex of the rat. II. Cortical and subcortical afferents

In order to compare the frontal cortex of rat and macaque monkey, cortical and subcortical afferents to subdivisions of the medial frontal cortex (MFC) in the rat were analyzed with fluorescent retrograde tracers. In addition to afferent inputs common to the whole MFC, each subdivision of the MFC has a specific pattern of afferent connections. The dorsally situated precentral medial area (PrCm) was the only area to receive inputs from the somatosensory cortex. The specific pattern of afferents common to the ventrally situated prelimbic (PL) and infralimbic (IL) areas included projections from the agranular insular cortex, the entorhinal and piriform cortices, the CA1-CA2 fields of the hippocampus, the subiculum, the endopiriform nucleus, the amygdalopiriform transition, the amygdalohippocampal area, the lateral tegmentum, and the parabrachial nucleus. In all these structures, the number of retrogradely labeled cells was larger when the injection site was located in area IL. The dorsal part of the anterior cingulate area (ACd) seemed to be connectionally intermediate between the adjacent areas PrCm and PL; it receives neither the somatosensory inputs characteristic of area PrCm nor the afferents characteristic of areas PL and IL, with the exception of the afferents from the caudal part of the retrosplenial cortex. A comparison of the pattern of afferent and efferent connections of the rat MFC with the pattern of macaque prefrontal cortex suggests that PrCm and ACd areas share some properties with the macaque premotor cortex, whereas PL and IL areas may have characteristics in common with the cingulate or with medial areas 24, 25, and 32 and with orbital areas 12, 13, and 14 of macaques.

Androgen and estrogen receptors coexist within individual neurons in the brain of the Syrian hamster.

Many aspects of reproductive neuroendocrine function and sexual behavior are responsive to both androgens and estrogens, suggesting that receptors for these steroid hormones may reside within single cells in brain regions that control reproductive function. We determined the distribution of estrogen receptor-containing neurons in 40-microns coronal brain sections in gonadectomized, DHT-treated male Syrian hamsters using immunocytochemistry with the H222 antibody (10 micrograms/ml; Abbott Laboratories). Subsequently, we colocalized estrogen receptors with androgen receptors using the PG-21 antibody (0.5 microgram/ml; G.S. Prins). In males, the distribution of estrogen receptor-containing neurons was similar to that reported previously for the female hamster. Colocalization of androgen and estrogen receptor immunoreactivity was observed in brain regions that contain numerous androgen and estrogen receptor-positive neurons, including subdivisions of the medial preoptic area, bed nucleus of the stria terminals, ventromedial nucleus of the hypothalamus, and the amygdalohippocampal area. Single-labelled estrogen receptor-containing neurons were most numerous in the amygdalohippocampal area and the rostral medial preoptic nucleus; androgen receptor-immunoreactive cells were most abundant in the ventral premammillary nucleus and the lateral septum. These data suggest the potential of androgens and estrogens to influence neuronal function within individual steroid receptor-containing neurons of the hamster limbic system.

Two types of cholinergic projections to the rat amygdala

The cholinergic innervation of the rat amygdala was studied immunohistochemically with antibodies against choline acetyltransferase and the low affinity p75 nerve growth factor receptor in normal rats and in rats lesioned with an immunotoxin, 192 IgG-saporin, directed against the p75 nerve growth factor receptor. The density of choline acetyltransferase-positive fibers was high in the nucleus of the lateral olfactory tract, the basolateral nucleus, and the amygdalohippocampal area; medium in the lateral nucleus, the cortical nucleus, the accessory basal nucleus, the periamygdaloid cortex, and the anterior amygdaloid area; and low in the medial and central nuclei. Nerve growth factor receptor-positive fibers were of medium density in the lateral nucleus, the accessory basal nucleus, the cortical nucleus, the anterior amygdaloid area, the periamygdaloid cortex, and the amygdalohippocampal area. The medial nucleus and the central nucleus displayed a low density of nerve growth factor receptor-positive fibers. The basolateral nucleus and the nucleus of the lateral olfactory tract also contained a low density of nerve growth factor receptor-positive fibers even though the two nuclei displayed the highest density of choline acetyltransferase-positive fibers in the amygdala. Injections of 192 IgG-saporin induced a complete loss of cholinergic nerve growth factor receptorpositive neurons in the basal forebrain but spared a subpopulation of nerve growth factor receptornegative cholinergic neurons in the nucleus basalis-substantia innominata complex. Following 192 IgG-saporin injections, choline acetyltransferase-positive and acetylcholinesterase-positive fibers were essentially unchanged in the nucleus of the lateral olfactory tract and the basolateral nucleus and showed a partial reduction in the remaining nuclei of the amygdaloid complex. Cholinergic fibers emanating from cholinergic cell group 4 neurons reached the amygdala via the stria terminalis and the ventral amygdalofugal pathway. These observations indicate that two amygdaloid nuclei, the nucleus of the lateral olfactory tract and the basolateral nucleus, receive their cholinergic projections predominantly, if not exclusively, from nerve growth factor receptor-negative cholinergic neurons whereas all remaining amygdaloid regions receive fibers from nerve growth factor receptor-negative as well as nerve growth factor receptor-positive cholinergic neurons.

Effect on food intake and body weight of lesions in and adjacent to the posterodorsal amygdala in rats

Bilateral lesions centered in the posterodorsal amygdala of female rats resulted in hyperphagia and excessive weight gain. The brain damage extended posteriorly through the amygdalohippocampal area and into the ventral hippocampus and subiculum. Lesions centered in the ventral hippocampal formation had a less pronounced, although still significant, effect on body weight. Damage to large areas of the amygdala, including the anterior, basolateral, and corticomedial groups of nuclei, was without effect. A serial reconstruction of overlapping areas of destruction for both effective and ineffective lesions is presented.

The distribution of GABAergic cells, fibers, and terminals in the monkey amygdaloid complex: an immunohistochemical and in situ hybridization study

The primate amygdaloid complex is a prominent structure in the medial temporal lobe that comprises a variety of cytoarchitectonically distinct nuclei and cortical regions. The present study employed immunohistochemical and in situ hybridization techniques to determine the distribution of GABAergic cells, fibers, and terminals in the macaque monkey amygdala. Using a monoclonal antibody to GABA, immunoreactive neurons were observed throughout the amygdaloid complex (constituting approximately 20% of the neurons in the lateral nucleus), with higher densities located in the intercalated nuclei, amygdalohippocampal area, and posterior cortical nucleus. The lowest densities of labeled cells were observed in the central and medial nuclei. Interestingly, despite the low number of GABA-immunoreactive neurons, the terminal density in the central nucleus was among the highest in the amygdala. The GABAergic neurons in the amygdala were heterogeneous in morphology, and three general classes of immunopositive aspiny cells were observed. Using mRNA probes for glutamic acid decarboxylase (GAD: GAD65 and GAD67), in situ hybridization demonstrated distributions of labeled cells that generally replicated the immunohistochemical findings. One exception was in the central nucleus where, in contrast to the low number of immunohistochemically labeled cells, both GAD probes labeled large numbers of neurons. These studies on the organization of GABAergic circuits in the primate amygdala are significant because alterations of function in the human amygdala have been implicated in the pathogenesis of temporal lobe epilepsy and in the etiology of affective and other behavioral disorders. The present study provides baseline information with which to evaluate the role of GABAergic systems in amygdala-mediated behaviors and the potential contribution of GABAergic dysfunction in amygdala-associated disorders.

Hypothalamic knife cuts that disrupt mating in male gerbils sever efferents and forebrain afferents of the sexually dimorphic area.

The sexually dimorphic area (SDA) of the gerbil hypothalamus is essential for male sexual behavior. To determine (a) if the SDA can affect mating via laterally projecting axons and (b) which SDA afferents might affect mating, male gerbils were given bilateral, parasagittal knife cuts lateral to the medial or lateral SDA. Others were given cuts with a knife coated with horseradish peroxidase to label cells of which axons were cut. Medial cuts eliminated mating and consistently labeled cells in the medial SDA. Lateral cuts did neither. Medial cuts also labeled more cells in the ventral part of the lateral septal nucleus, the encapsulated part of the bed nucleus of the stria terminalis, the medial nucleus of the amygdala, the amygdalohippocampal area, and the ventral premammillary nucleus than lateral cuts did. Thus, medial cuts may disrupt mating by severing SDA efferents or by severing SDA afferents from 1 or more of these 5 sites.

The functional anatomy of limbic status epilepticus in the rat. II. The effects of focal deactivation

Limbic status epilepticus was induced in awake, unrestrained rats by electrically stimulating the anterior piriform cortex or the basal amygdaloid nucleus for about 40 min. As described in the preceding article (White and Price, 1993), one of four stable forms of status may be induced. Each form is characterized on the basis of its behavioral and electroencephalographic manifestations, and its distinct patterns of 14C-2-deoxyglucose uptake and Fos-like immunoreactivity. This study was directed at identifying the epileptogenic foci of the two major forms of status, types II and III, by deactivating the basal amygdaloid nucleus, ventral hippocampal formation, amygdalohippocampal area, or anterior piriform cortex during these seizure states. Infusions of the local anesthetic lidocaine, the GABA agonist muscimol, or a vehicle solution alone were made into each of these structures during ongoing type II or type III status. The major finding is that deactivation of the basal amygdaloid nucleus terminated both types of status. This indicates that the basal nucleus is primarily responsible for the generation of widespread status epilepticus activity. Deactivation of the ventral hippocampal formation did not terminate the subconvulsive levels of status, but did prevent the recurrent development of sustained seizures with facial and forelimb clonus that characterize type III status. These models of status epilepticus may be particularly important for understanding seizure mechanisms that are not dependent upon the hippocampal formation. The possible clinical relevance of these findings is discussed in relation to temporal lobe epilepsy.

The functional anatomy of limbic status epilepticus in the rat. I. Patterns of 14C-2-deoxyglucose uptake and Fos immunocytochemistry

Limbic status epilepticus was induced in awake, unrestrained rats by electrically stimulating the olfactory cortex or the basal amygdaloid nucleus for about 40 min. One of four stable forms of status was induced, which were distinguished on the basis of their behavioral and EEG manifestations, and their distinct patterns of 14C-2-deoxyglucose uptake and Fos-like immunoreactivity. Type I status was characterized by sporadic EEG discharges and the activation of the amygdalohippocampal area, but had no overt behavioral manifestation. Type II status involved incessant exploratory behaviors, single EEG discharges, and the additional activation of the basal amygdaloid nucleus, some of its efferent projections, and parts of the olfactory cortex. Type III status included all of these same patterns, plus the episodic development of ictal EEG activity associated with facial and forelimb clonus, and the concurrent recruitment of the entire amygdala, ventral hippocampal formation, prefrontal, insular, and olfactory cortices, and related subcortical structures. Type IV status was characterized by generalized clonus, unremitting ictal EEG discharges, and the additional activation of most of the dorsolateral neocortex, neostriatum, and thalamus. In each case of status type I, II, or III, the same anatomical structures that displayed high levels of 14C-2-deoxyglucose uptake also contained many cells that were immunoreactive for Fos, with the exception of the parataenial and mediodorsal thalamic nuclei and the substantia nigra pars reticularis. Thus, the overall patterns of 14C-2-deoxyglucose uptake and Fos-like immunoreactivity from the same animals displayed a remarkable degree of correspondence. The major results indicate that different levels of status are related to the activation of discrete epileptogenic foci, and the capacity of such foci to interact with a distinct set of interconnected anatomical structures. It is suggested that the behavioral manifestations of limbic status epilepticus may be explained by influences of limbic structures in the ventral forebrain upon lower motor elements in the brainstem and spinal cord, without the participation of the "pyramidal" motor system.

Hyperphagia and obesity in female rats with temporal lobe lesions

Damage to the temporal lobes in cats, dogs, and primates has long been known to result in hyperphagia and obesity, but research into the role of this area of the brain in feeding behavior has largely been neglected because of an inability to produce similar results in rats. The present study reports hyperphagia and obesity in female rats with small electrolytic lesions centered in the posterodorsal amygdala. Daily food intake more than doubled in the first few days after surgery and mean weight gain was more than four times that observed in animals with sham lesions during the first 26 days. The rats with lesions were not hyperresponsive to a switch in diets (lab chow to high-fat, and back). In all animals that gained abnormal amounts of weight, the posterior extent of the lesions extended through the amygdalohippocampal area into the ventral hippocampal formation. The results suggest that the temporal lobe is an important extrahypothalamic site for the regulation of food intake in rodents.

Localization of oxytocin receptor messenger ribonucleic acid in the rat brain.

The expression of oxytocin receptor (OT-R) mRNA in the rat central nervous system was examined by in situ hybridization histochemistry using cRNA probe. Wide distribution of cells expressing OT-R mRNA was observed not only in the hypothalamus, but also in other regions. There were high levels of OT-R mRNA in the anterior olfactory nuclei, tenia tecta, olfactory tubercle, rostral most region of the frontal cortex, piriform cortex, layers 2 and 3 of the neocortex, bed nucleus of the stria terminalis, anterior medial preoptic nucleus (AV3V region), magnocellular preoptic nucleus, supraoptic nucleus, paraventricular hypothalamic nucleus, retrochiasmatic nucleus, ventromedial hypothalamic nucleus, paraventricular thalamic nucleus, central amygdaloid nucleus, medial amygdaloid nucleus, posterior cortical amygdaloid nucleus, amygdalohippocampal area, subiculum, prepositus hypoglossal nucleus, and dorsal motor nucleus of vagus. In most regions of the brain, our findings concurred with those obtained by receptor binding autoradiography using a ligand specific to OT. However, in the inferior olive nucleus, OT-R mRNA was not detected despite an abundance of binding sites showed by receptor binding autography. Despite this discrepancy OT appears to have central nervous system functions in addition to its hormonal functions.

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.