PubMed Health⌕ Search

Biomedical subjects

R B Simerly

Publications and source records attributed to R B Simerly.

At least 37 records · Page 2Linked to original sources
PubMed1993

Identification of a receptor for gamma melanotropin and other proopiomelanocortin peptides in the hypothalamus and limbic system.

Corticotropin (ACTH) and melanotropin (MSH) peptides (melanocortins) are produced not only in the pituitary but also in the brain, with highest concentrations in the arcuate nucleus of the hypothalamus and the commisural nucleus of the solitary tract. We have identified a receptor for MSH and ACTH peptides that is specifically expressed in regions of the hypothalamus and limbic system. This melanocortin receptor (MC3-R) is found in neurons of the arcuate nucleus known to express proopiomelanocortin (POMC) and in a subset of the nuclei to which these neurons send projections. The MC3-R is 43% identical to the MSH receptor present in melanocytes and is strongly coupled to adenylyl cyclase. Unlike the MSH or ACTH receptors, MC3-R is potently activated by gamma-MSH peptides, POMC products that were named for their amino acid homology with alpha- and beta-MSH, but lack melanotropic activity. The primary biological role of the gamma-MSH peptides is not yet understood. The location and properties of this receptor provide a pharmacological basis for the action of POMC peptides produced in the brain and possibly a specific physiological role for gamma-MSH.

Adenylyl Cyclases↗
PubMed1992

Connections of the posterior nucleus of the amygdala.

The connections of a relatively homogeneous band of neurons in the caudal amygdala have been examined with anterograde and retrograde axonal tracing methods in the rat. This region, called here the posterior nucleus of the amygdala (PA), corresponds in part to an area that has been referred to as the cortico-amygdaloid transition area, posterior part of the medial nucleus of the amygdala, amygdalo-hippocampal transition area, and posteromedial basal nucleus. Experiments with fluorogold and phaseolus vulgaris leucoagglutinin (PHAL) indicate that the major neuronal input to the PA arises in the ventral premammillary nucleus, and that substantial projections also arise in olfactory-related areas such as the medial nucleus of the amygdala, bed nucleus of the accessory olfactory tract, and posterior cortical nucleus of the amygdala, as well as in the ventral subiculum and adjacent parts of hippocampal field CA1. Other seemingly minor inputs, including cholinergic fibers from the substantia innominata, dopaminergic fibers from the ventral tegmental area, and serotoninergic fibers from the dorsal nucleus of the raphe, were also identified. The efferent projections of the PA as determined with the PHAL method appear to follow five major routes: 1) a relatively small group of laterally directed fibers innervates the dorsal endopiriform nucleus, and a few of these fibers reach cortical area TR and the lateral entorhinal area; 2) another small group of fibers courses medially to innervate the ventral subiculum and adjacent parts of field CA1; 3) many fibers course ventrally to innervate the outer molecular layer of the medial part of the posterior cortical nucleus of the amygdala; 4) a moderate group of fibers courses rostrally to innervate primarily the posterodorsal part of the medial nucleus of the amygdala, although some fibers continue on to end less densely in rostral parts of the medial nucleus of the amygdala before leaving the amygdala through the ansa peduncularis; and 5) the major output of the PA courses through the stria terminalis. One branch of this pathway massively innervates the principal nucleus of the bed nuclei of the stria terminalis before entering the medial hypothalamus, where it ends massively in the anteroventral periventricular and medial preoptic nuclei, ventrolateral part of the ventromedial nucleus and adjacent parts of the basal lateral hypothalamic area, and ventral premammillary nucleus. The other branch sends fibers to the ventral lateral septal nucleus, nucleus accumbens, olfactory tubercle, and infralimbic area of the prefrontal cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Amygdala↗
PubMed1992

Projections of the ventral premammillary nucleus.

The projections of the ventral premammillary nucleus (PMv) have been examined with the Phaseolus vulgaris leucoagglutinin (PHAL) method in adult male rats. The results indicate that the nucleus gives rise to two major ascending pathways and a smaller descending pathway. One large ascending pathway terminates densely in most regions of the periventricular zone of the hypothalamus, with the notable exception of the suprachiasmatic, suprachiasmatic preoptic, and median preoptic nuclei. This pathway is in a position to influence directly many cell groups known to regulate anterior pituitary function. The second large pathway ascends through the medial zone of the hypothalamus and densely innervates the ventrolateral part of the ventromedial nucleus and adjacent basal parts of the lateral hypothalamic area, medial preoptic nucleus, principal nucleus of the bed nuclei of the stria terminalis, ventral lateral septal nucleus, posterodorsal part of the medial nucleus of the amygdala, posterior nucleus, and immediately adjacent regions of the posterior cortical nucleus of the amygdala. It is already known that these regions are major components of the sexually dimorphic circuit, and, interestingly, that they provide the major neural inputs to the PMv. The smaller descending projection from the PMv seems to innervate preferentially the posterior hypothalamic nucleus, although a small number of fibers appear to end in the tuberomammillary nucleus, supramammillary nucleus, specific regions of the medial mammillary nucleus, interfascicular nucleus, interpeduncular nucleus, periaqueductal gray, dorsal nucleus of the raphe, laterodorsal tegmental nucleus, Barrington's nucleus, and locus coeruleus. Relatively sparse terminal fields associated with ascending fibers were also observed in the dorsomedial nucleus of the hypothalamus; in the nucleus reuniens, parataenial nucleus, paraventricular nucleus of the thalamus, and mediodorsal nucleus; in the central nucleus of the amygdala, anterodorsal part of the medial nucleus of the amygdala, posterior part of the basomedial nucleus of the amygdala; and in the ventral subiculum and adjacent parts of hippocampal field CA1, and the infralimbic and prelimbic areas of the medial prefrontal cortex. Taken as a whole, the evidence suggests that the PMv receives two major inputs--one from the sexually dimorphic circuit, and the other from the blood in the form of gonadal steroid hormones--and gives rise to two major outputs: one (perhaps feed-forward) to the neuroendocrine (periventricular) zone of the hypothalamus, and the other (perhaps feed-back) to the sexually dimorphic circuit.

Animals↗
PubMed1992

The G-protein-coupled receptor kinases beta ARK1 and beta ARK2 are widely distributed at synapses in rat brain.

The beta-adrenergic receptor kinase (beta ARK) phosphorylates the agonist-occupied beta-adrenergic receptor to promote rapid receptor uncoupling from Gs, thereby attenuating adenylyl cyclase activity. Beta ARK-mediated receptor desensitization may reflect a general molecular mechanism operative on many G-protein-coupled receptor systems and, particularly, synaptic neurotransmitter receptors. Two distinct cDNAs encoding beta ARK isozymes were isolated from rat brain and sequenced. The regional and cellular distributions of these two gene products, termed beta ARK1 and beta ARK2, were determined in brain by in situ hybridization and by immunohistochemistry at the light and electron microscopic levels. The beta ARK isozymes were found to be expressed primarily in neurons distributed throughout the CNS. Ultrastructurally, beta ARK1 and beta ARK2 immunoreactivities were present both in association with postsynaptic densities and, presynaptically, with axon terminals. The beta ARK isozymes have a regional and subcellular distribution consistent with a general role in the desensitization of synaptic receptors.

Amino Acid Sequence↗
PubMed1991

Regulation of estrogen receptor messenger ribonucleic acid in rat hypothalamus by sex steroid hormones.

Sex steroid hormone receptors are thought to mediate the actions of their respective hormones by functioning as ligand-activated nuclear transcription factors that alter the expression of specific sets of hormone-responsive genes. Particularly high densities of estrogen receptor (ER)-containing neurons are located in the arcuate nucleus (ARH) and ventrolateral part of the ventromedial nucleus (VMHvl) of the hypothalamus, and these cell groups are thought to play key roles in the neuroendocrine control of reproductive function. Thus, hormonal regulation of ER gene expression in ARH and VMHvl neurons represents a direct mechanism by which circulating sex steroids could affect the responsiveness of these neurons to hormonal activation. We used in situ hybridization histochemistry to evaluate the influence of estradiol and testosterone on levels of ER mRNA within the ARH and VMHvl of adult male and female rats. In female rats, estradiol treatment reduced levels of ER mRNA in the ARH and VMHvl within 24 h relative to levels in both ovariectomized control animals and intact estrous females. Comparable results were obtained in male rats, except that testosterone did not significantly attenuate ER mRNA hybridization in the VMHvl until after 3 days of hormone treatment, and only a minor decrease was noted in the ARH, which was not statistically significant. In both male and female animals, the overall density of labeling found over individual cells in emulsion-dipped autoradiograms was consistently lower in hormone-treated animals compared with that over cells in gonadectomized controls, suggesting that the observed decreases in ER mRNA hybridization measured over the ARH and VMHvl are due to changes in cellular levels of ER mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Distribution of androgen and estrogen receptor mRNA-containing cells in the rat brain: an in situ hybridization study.

The distribution of cells that express mRNA encoding the androgen (AR) and estrogen (ER) receptors was examined in adult male and female rats by using in situ hybridization. Specific labeling appeared to be largely, if not entirely, localized to neurons. AR and ER mRNA-containing neurons were widely distributed in the rat brain, with the greatest densities of cells in the hypothalamus, and in regions of the telencephalon that provide strong inputs in the medial preoptic and ventromedial nuclei, each of which is thought to play a key role in mediating the hormonal control of copulatory behavior, as well as in the lateral septal nucleus, the medial and cortical nuclei of the amygdala, the amygdalohippocampal area, and the bed nucleus of the stria terminalis. Heavily labeled ER mRNA-containing cells were found in regions known to be involved in the neural control of gonadotropin release, such as the anteroventral periventricular and the arcuate nuclei, but only a moderate density of labeling for AR mRNA was found over these nuclei. In addition, clearly labeled cells were found in regions with widespread connections throughout the brain, including the lateral hypothalamus, intralaminar thalamic nuclei, and deep layers of the cerebral cortex, suggesting that AR and ER may modulate a wide variety of neural functions. Each part of Ammon's horn contained AR mRNA-containing cells, as did both parts of the subiculum, but ER mRNA appeared to be less abundant in the hippocampal formation. Moreover, AR and ER mRNA-containing cells were also found in olfactory regions of the cortex and in both the main and accessory olfactory bulbs. AR and ER may modulate nonolfactory sensory information as well since labeled cells were found in regions involved in the central relay of somatosensory information, including the mesencephalic nucleus of the trigeminal nerve, the ventral thalamic nuclear group, and the dorsal horn of the spinal cord. Furthermore, heavily labeled AR mRNA-containing cells were found in the vestibular nuclei, the cochlear nuclei, the medial geniculate nucleus, and the nucleus of the lateral lemniscus, which suggests that androgens may alter the central relay of vestibular and auditory information as well. However, of all the regions involved in sensory processing, the heaviest labeling for AR and ER mRNA was found in areas that relay visceral sensory information such as the nucleus of the solitary tract, the area postrema, and the subfornical organ. We did not detect ER mRNA in brainstem somatic motoneurons, but clearly labeled AR mRNA-containing cells were found in motor nuclei associated with the fifth, seventh, tenth, and twelfth cranial nerves. Similarly, spinal motoneurons contained AR but not ER mRNA.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Hormonal control of neuropeptide gene expression in sexually dimorphic olfactory pathways.

An abundance of experimental literature has established that gonadal steroid hormones are responsible for the sexual differentiation of neural circuitry, mediating a variety of reproductive behaviors and physiological mechanisms. These same hormones regulate the expression of reproductive function in the adult and may influence the responsiveness of the brain to specific olfactory cues. The recent demonstration that the expression of the neuropeptide cholecystokinin is activationally regulated by estrogen at the mRNA level, within a sexually dimorphic population of neurons in the medial amygdala, suggests a possible cellular mechanism for the hormonal modulation of olfactory information relayed along the vomeronasal pathway to the hypothalamus.

Animals↗
PubMed1989

Studies on the cellular architecture of the bed nuclei of the stria terminalis in the rat: II. Chemoarchitecture.

In a companion paper (Ju and Swanson; J. Comp. Neurol. 280:587-602, '89) we described a parcellation scheme for the bed nuclei of the stria terminalis (BST) that was based on cytoarchitectonic criteria. In the work reported here, antisera to the neuropeptides corticotropin-releasing hormone, neurotensin, galanin, substance P, and cholecystokinin were used to determine the extent to which immunostained neuronal cell bodies and presumed terminal fields are correlated with this cytoarchitectonic scheme in the adult male rat. The results confirm the validity of the cytoarchitectonic parcellation and provide additional chemoarchitectonic criteria for determining the (as yet still somewhat arbitrarily defined) border between the BST and the ventrally adjacent preoptic region, for distinguishing between the anterior and posterior divisions of the BST, and for identifying and distinguishing between the particular cell groups or nuclei within each division. The projections of each neuropeptide-containing cell group in various parts of the BST remain to be determined, as do the precise origins of the localized immunoreactive terminal fields identified here.

Animals↗
PubMed1989

Hormonal control of the development and regulation of tyrosine hydroxylase expression within a sexually dimorphic population of dopaminergic cells in the hypothalamus.

In situ hybridization histochemistry was used to examine the development and regulation of tyrosine hydroxylase (TH) mRNA within the sexually dimorphic population of dopaminergic cells in the anteroventral periventricular nucleus (AVPv) of the hypothalamus. The AVPv contains over 3 times as many TH mRNA-containing cells in female rats, compared with males. This sexual dimorphism appears to be dependent on perinatal levels of gonadal steroids since orchidectomy of newborn males increased, and treatment of newborn females with testosterone decreased, the number of TH mRNA-containing cells detected within the AVPv. In addition, circulating gonadal steroids appear to downregulate TH expression within these cells in both adult male and female rats. In adult male animals, gonadectomy increased the number of TH mRNA cells in the AVPv within 7 days. Similarly, estradiol treatment prevented the increase in the number of TH mRNA-containing cells within the AVPv seen in ovariectomized female rats. No sexual differences were detected in the number of TH mRNA-containing cells within the suprachiasmatic preoptic nucleus, located just ventral to the AVPv. These findings indicate that perinatal gonadal steroids influence the number of cells within the AVPv that express TH in detectable amounts by determining the number of cells that are capable of producing sufficient quantities of TH message, as opposed to sex-specific alterations in the post-translational mechanisms. In the adult, circulating gonadal steroids appear to downregulate TH expression within these cells suggesting that testosterone and/or estrogen may exert a sustained influence on the biosynthetic activity of this sexually dimorphic population of dopaminergic cells.

Animals↗
PubMed1989

Connectivity of striatal grafts implanted into the ibotenic acid-lesioned striatum--III. Efferent projecting graft neurons and their relation to host afferents within the grafts.

Efferent projections of intrastriatally implanted striatal neurons have been studied using a combination of anterograde and retrograde axonal tracers. Adult rats subjected to a unilateral ibotenic acid lesion of the head of the caudate putamen received cell suspension grafts obtained from 14 15-day-old striatal primordia. Three and a half to 20 months after transplantation the rats received either intratransplant injections of the anterograde axonal tracer Phaseolus vulgaris leucoagglutinin or injections of fluorescent retrograde tracers. Fluoro-Gold and rhodamine-labelled latex beads, into the host globus pallidus and substantia nigra. Injections of Phaseolus vulgaris leucoagglutinin located entirely within the grafts labelled axons that ramified extensively within the tissue itself, as well as axons that extended caudally, across the graft host border, along the myelinated fascicles of the internal capsule to arborize in the medial parts of the host globus pallidus. A few axons also reached the entopeduncular nucleus. Injections of Fluoro-Gold into the host globus pallidus labelled large numbers of graft neurons, which had a prominent patchy distribution and were most abundant in the caudal portions of the grafts. Clear retrograde labelling was also seen after injection of Fluoro-Gold or rhodamine beads into the host substantia nigra, although the number of labelled graft neurons was 30-50 times lower than that seen after pallidal injections. Combined injections of Fluoro-Gold into the pallidus and rhodamine beads into the nigra showed that the vast majority of cells labelled from the nigra were also labelled by Fluoro-Gold from the pallidus. In some of the grafted and Fluoro-Gold-injected animals, the fetal donor tissue had been labelled with [3H]thymidine prior to transplantation. Many examples of neurons labelled with both [3H]thymidine and Fluoro-Gold were found after tracer injections into the host globus pallidus, and double-labelled neurons were identified also after Fluoro-Gold injections into the host substantia nigra. In several animals retrograde tracing was combined with labelling of host dopaminergic afferents (by tyrosine hydroxylase immunohistochemistry) and cortical afferents (by injections of Phaseolus vulgaris leucoagglutinin into the host frontal cortex). Comparison of adjacent sections revealed a striking overlap between the patches of Fluoro-Gold-labelled graft neurons (labelled from the host pallidum) and the dense patches of tyrosine hydroxylase-positive terminals. In addition, many of the Fluoro-Gold-labelled cell patches received a high density of cortical afferents labelled by Phaseolus vulgaris leucoagglutinin.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Estrogen differentially regulates neuropeptide gene expression in a sexually dimorphic olfactory pathway.

The posterodorsal part of the medial nucleus of the amygdala (MeAp) receives its major sensory input from the accessory olfactory bulb and projects massively to the medial preoptic nucleus and other sexually dimorphic hypothalamic nuclei thought to play key roles in mediating steroid-sensitive reproductive functions. A combined axonal transport/double-immunohistochemical method was used to show that at least one-quarter of the cholecystokinin-immunoreactive cells in the MeAp cocontain substance P and that a substantial proportion of these cells project to the medial preoptic nucleus. In situ hybridization histochemistry was then used to demonstrate that estrogen regulates the expression of preprocholecystokinin in these cells at the mRNA level in male and female rats. In contrast, levels of preprotachykinin mRNA within the MeAp do not appear to be sensitive to acute changes in circulating gonadal steroids in either sex. Although posttranscriptional regulation of mRNA stability may contribute to the observed effects, it appears likely that estrogen stimulates preprocholecystokinin expression within the MeAp by selectively inducing transcription of the corresponding gene, thereby altering the relative amounts of cholecystokinin and substance P coexpressed within individual neurons of the MeAp that project to the hypothalamus.

Amygdala↗
PubMed1988

Distribution of opioid peptides in the preoptic region: immunohistochemical evidence for a steroid-sensitive enkephalin sexual dimorphism.

The distribution of cells and fibers that contain opioid peptides within the preoptic region of the rat was examined immunohistochemically. Cells and/or fibers that contain peptides derived from each of the three major opioid peptide families were differentially stained by using antisera that recognize unique derivatives of each precursor molecule and do not cross-react with members of the other opioid peptide families. A beta-endorphin (beta E) antiserum was used to stain fibers that contain peptides derived from the proopiomelanocortin molecule, and dynorphin-containing cells were identified by using an antiserum directed toward dynorphin B (Dyn B) that does not show detectable cross-reactivity with enkephalin-related peptides. An antiserum raised against peptide E (PE), which does not appear to cross-react significantly with dynorphin peptides, was used to localize enkephalin cells and fibers. Each family of opioid peptides showed a unique distribution in the preoptic region. beta E-immunoreactive fibers were primarily localized to the preoptic part of the periventricular nucleus, with moderate densities of fibers contained in the anteroventral periventricular nucleus (AVPv) and medial preoptic nucleus (MPN). Dyn B-immunoreactive fibers showed a somewhat more uniform distribution throughout the region, and only a few Dyn B-stained cells bodies were found within the medial preoptic area. In contrast, the preoptic region contained hundreds of PE-immunoreactive cells, which were particularly numerous within the AVPv, MPN, and anterodorsal preoptic nucleus. The AVPv and MPN also contained discretely localized plexuses of PE-stained fibers. Although the overall distributions of opioid peptide-containing fibers within the preoptic region were quite similar in male and female rats, differential distributions of fibers were found in certain nuclei such as the AVPv and MPN, and they were correlated with previously identified cytoarchitectonic sexual dimorphisms. Such differential distributions were particularly distinct for enkephalin-containing fibers. Although the AVPv is larger in female rats, it contained more PE-immunoreactive cell bodies in male rats, and we have shown here that this sexual dimorphism appears to be at least partially dependent on perinatal levels of gonadal steroids. In contrast, no difference in the number of PE-stained cells was found within the anterodorsal preoptic nucleus of male and female animals, indicating that sexual differences are not a general characteristic of enkephalinergic cells in the preoptic region of the rat.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Estrogen-concentrating hypothalamic and limbic neurons project to the medial preoptic nucleus.

Estrogen-concentrating neurons that project to the medial preoptic nucleus of the male rat were found to be numerous in limbic and hypothalamic cell groups including the ventral part of the lateral septum, bed nucleus of the stria terminalis, medial amygdaloid nucleus, the ventromedial nucleus, and the amygdalohippocampal zone. This steroid-sensitive circuitry is implicated in the activation of reproductive processes in the male.

Animals↗
PubMed1988

Projections of the medial preoptic nucleus: a Phaseolus vulgaris leucoagglutinin anterograde tract-tracing study in the rat.

The projections of the medial preoptic nucleus (MPN) were examined by making injections of the anterogradely transported lectin Phaseolus vulgaris leucoagglutinin (PHA-L) into the MPN and charting the distribution of labeled fibers. The evidence indicates that the MPN projects extensively to widely distributed regions in both the forebrain and brainstem, most of which also supply inputs to the nucleus. An important neuroendocrine role for the MPN is underscored by its extensive projections to almost all parts of the periventricular zone of the hypothalamus, including the anteroventral periventricular, anterior part of the periventricular, paraventricular (PVH), and arcuate nuclei, and a role in autonomic mechanisms is indicated by projections to such regions as the dorsal and lateral parvicellular parts of the PVH, the lateral parabrachial nucleus, and the nucleus of the solitary tract. Other projections of the MPN suggest participation in the initiation of specific motivated behaviors. For example, inputs to two nuclei of the medial zone of the hypothalamus, the ventromedial and dorsomedial nuclei, may be related to the control of reproductive and ingestive behaviors, respectively, although the possible functional significance of a strong projection to the ventral premammillary nucleus is presently unclear. The execution of these behaviors may involve activation of somatomotor regions via projections to the substantia innominata, zona incerta, ventral tegmental area, and pedunculopontine nucleus. Similarly, inputs to other regions that project directly to the spinal cord, such as the periaqueductal gray, the laterodorsal tegmental nucleus, certain medullary raphe nuclei, and the magnocellular reticular nucleus may also be involved in modulating somatic and/or autonomic reflexes. Finally, the MPN may influence a wide variety of physiological mechanisms and behaviors through its massive projections to areas like the ventral part of the lateral septal nucleus, the bed nucleus of the stria terminalis, the lateral hypothalamic area, the supramammillary nucleus, and the ventral tegmental area, all of which have extensive connections with regions along the medial forebrain bundle. Although the PHA-L method does not allow a clear demonstration of possible differential projections from each subdivision of the MPN, our results suggest that each of them does give rise to a unique pattern of outputs.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

The neuronal mineralocorticoid receptor as a mediator of glucocorticoid response.

The cloning of the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR) cDNAs provides a basis for understanding the actions of glucocorticoids in the central nervous system. Structural evidence is presented for the identity of the type I corticosteroid binding site as the MR expressed in the brain. This identification is supported by the anatomical distribution of MR mRNA, determined by in situ hybridization histochemistry, which parallels the steroid autoradiographic localization of the type I sites. An in vitro assay for MR and GR function demonstrates that these receptors respond to different levels of glucocorticoid, suggesting that together they confer a larger dynamic range of sensitivity to this hormone. These studies lead to a new hypothesis for glucocorticoid action in the central nervous system.

Animals↗
PubMed1988

Estrous cycle variations in levels of cholecystokinin immunoreactivity within cells of three interconnected sexually dimorphic forebrain nuclei. Evidence for a regulatory role for estrogen.

The central part of the medial preoptic nucleus (MPNc), the encapsulated part of the bed nucleus of the stria terminalis (BSTe), and the posterodorsal part of the medial nucleus of the amygdala (MeAp) are all though to be involved in the neural control of female reproductive behavior, as well as other neuroendocrine mechanisms. Although the developmental importance of gonadal steroids during the perinatal period on these sexual dimorphisms is well known, an understanding of possible activational effects on these cell groups of circulating gonadal steroids in the adult is less clear. In the present study we evaluated the number of cholecystokinin (CCK)-immunoreactive cells present within MPNc, BSTe, and MeAp of regularly cycling female rats over the estrous cycle. In addition, the effects of ovariectomy and estrogen replacement on CCK staining were also examined. The number of CCK-immunoreactive cells within each cell group varied over the estrous cycle with the fewest cells present in animals sacrificed while in diestrus. Proestrous female rats showed a greater number of cells within each nucleus, while intermediate numbers were found for animals in estrus. These changes appear to be due, at least in part, to changes in levels of circulating estrogen, since subcutaneous implants of estradiol prevented the decline in the number of CCK-stained cells within MPNC, BSTe, and MeAp that was seen in untreated, ovariectomized female rats. Thus, the present findings support the hypothesis that levels of CCK within cells of these three sexually dimorphic cell groups are regulated by circulating gonadal steroids within a physiologically relevant time frame and may possibly contribute to the activation of female reproductive behavior as well as other neuroendocrine functions.

Amygdala↗
PubMed1987

Anatomical and electrophysiological evidence for a projection from the medial preoptic area to the 'mesencephalic and subthalamic locomotor regions' in the rat.

There is considerable physiological evidence indicating that the medial preoptic area plays an important role in neural circuits mediating ingestive, thermoregulatory, and reproductive behaviors, all of which involve foraging. The current series of anatomical and electrophysiological experiments was therefore designed to characterize a direct projection from the medial preoptic area to a region in the zona incerta just dorsal to the subthalamic nucleus, which appears to lie within the 'subthalamic locomotor region', and to the pedunculopontine nucleus, which lies within the 'mesencephalic locomotor region'. First, implants of the fluorescent tracer True blue were placed in the pedunculopontine nucleus, and retrogradely labeled neurons were consistently found in dorsal regions of the medial preoptic nucleus, anteroventral preoptic nucleus, rostral tip of the medial preoptic area, lateral parts of the medial preoptic area, and median preoptic nucleus. Second, combined retrograde-immunostaining experiments indicated that a small number of galanin-stained neurons in the rostral tip of the medial preoptic area project to the pedunculopontine nucleus, whereas in nearby regions some galanin- or neurotensin-stained neurons in the lateral preoptic area, and some neurotensin-stained neurons in the substriatal gray appear to project to the pedunculopontine nucleus, as do some neurotensin- or corticotropin releasing factor (CRF)-stained cells in the bed nucleus of the stria terminalis. Third, injections of the anterograde tracer Phaseolus vulgaris leukoagglutinin (PHA-L) into various parts of the medial preoptic area all labeled axons with terminal boutons in the caudal zona incerta and pedunculopontine nucleus. Fourth, single-pulse stimuli were delivered to the zona incerta and pedunculopontine nucleus and the location of antidromically activated neurons in the medial preoptic area was mapped using extracellular recordings. Somewhat less than one-third of the cells recorded from in the medial preoptic area were antidromically activated from either site and some 14% were influenced from both sites. The application of a reciprocal collision test to a small number of neurons suggested that at least some neurons in the medial preoptic area may send collaterals to both sites. And fifth, injections of procaine into the zona incerta were shown to block the antidromic activation of medial preoptic neurons by single-pulse stimulation of the pedunculopontine nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗