Electrophysiological investigation of cortico-hypothalamic relations in cats

Projections of different parts of the orbito-frontal cortex, the basal temporal cortex, and the hippocampus on hypothalamic nuclei were studied by recording focal responses in acute experiments on cats anesthetized with pentobarbital and chloralose. The proreal gyrus was shown to have local projections in the latero-dorsal zones of the preoptic region, in the rostral parts of the medial forebrain bundle, and also in the region of the lateral and posterior hypothalamus with the mammillary bodies. The orbital gyrus projects mainly to the latero-dorsal portions of the forebrain bundle, the latero-ventral part of the preoptic region, and the region of the lateral and latero-dorsal hypothalamic nuclei; projections from the orbital gyrus are relatively diffuse in character. The basal temporal cortex has diffuse projections in the central part of the preoptic region, in the latero-ventral parts of the medial forebrain bundle, and in the lateral mammillary body. No marked foci of activity were found in the hypothalamic structures during hippocampal stimulation. Diffuse projections of the hippocampus were traced in the ventral part of the preoptic region and the ventral regions of the medial forebrain bundle, and also in the lateral hypothalamus and in the lateral mammillary nucleus.A. M. Gor'kii Donetsk Medical Institute. Translated from Neirofiziologiya, Vol. 8, No. 4, pp. 358–365, July–August, 1976.     

大鼠下丘脑内一氧化氮合酶阳性神经元的分布

用ＮＡＤＰＨ－ｄ组织化学方法观察了大白鼠下丘脑内一氧化氮合酶（ＮＤＳ）阳性神经元的分布及形态特征。结果显示：在视上核、室旁核的大细胞部、环状核、穹窿周核、下丘脑外侧区、下丘脑腹内侧核、下丘脑背内侧核、乳头体区大部分核团均可见一氧化氮合酶阳性神经元聚集成团。在视前内侧区、视前外侧区、下丘脑前区、下丘脑背侧区、下丘脑后区、室周核、室旁核小细胞部及穹窿内可见散在的一氧化氮合酶阳性神经元。室周核内可见呈阳性反应的接触脑脊液神经元的胞体及突起。一氧化氮合酶阳性神经元大多可见突起,有的突起上可见１～２级分支,并可见膨体。下丘脑大部分区域内可见阳性神经纤维。弓状核内可见许多弧形纤维连于第三脑室室管膜和正中隆起。     

Immunohistochemical mapping of galanin-like neurons in the rat central nervous system

Using an antiserum generated in rabbits against synthetic galanin (GA) and the indirect immunofluorescence method, the distribution of GA-like immunoreactive cell bodies and nerve fibers was studied in the rat central nervous system (CNS) and a detailed stereotaxic atlas of GA-like neurons was prepared. GA-like immunoreactivity was widely distributed in the rat CNS. Appreciable numbers of GA-positive cell bodies were observed in the rostral cingulate and medial prefrontal cortex, the nucleus interstitialis striae terminalis, the caudate, medial preoptic, preoptic periventricular, and preoptic suprachiasmatic nuclei, the medial forebrain bundle, the supraoptic, the hypothalamic periventricular, the paraventricular, the arcuate, dorsomedial, perifornical, thalamic periventricular, anterior dorsal and lateral thalamic nuclei, medial and central amygdaloid nuclei, dorsal and ventral premamillary nuclei, at the base of the hypothalamus, in the central gray matter, the hippocampus, the dorsal and caudoventral raphe nuclei, the interpeduncular nucleus, the locus coeruleus, ventral parabrachial, solitarii and commissuralis nuclei, in the A1, C1 and A4 catechaolamine areas, the posterior area postrema and the trigeminal and dorsal root ganglia. Fibers were generally seen where cell bodies were observed. Very dense fiber bundles were noted in the septohypothalamic tract, the preoptic area, in the hypothalamus, the habenula and the thalamic periventricular nucleus, in the ventral hippocampus, parts of the reticular formation, in the locus coeruleus, the dorsal parabrachial area, the nucleus and tract of the spinal trigeminal area and the substantia gelatinosa, the superficial layers of the spinal cord and the posterior lobe of the pituitary. The localization of the GA-like immunoreactivity in the locus coeruleus suggests a partial coexistence with catecholaminergic neurons as well as a possible involvement of the GA-like peptide in a neuroregulatory role.     

Localization of proopiomelanocortin (POMC) immunoreactive neurons in the forebrain of the pig

The distribution of proopiomelanocortin (POMC)-immunoreactive neurons was examined in the forebrains of nine sexually mature female pigs by indirect biotin-avidin horseradish peroxidase immunocytochemistry. Primary antiserum against ovine beta-endorphin (Bioflex #BF-EP-3-1) yielded positive staining of neuronal perikarya and processes. Adjacent control sections treated either with primary antiserum preabsorbed with beta-endorphin or substituted with normal rabbit serum lacked specific staining. POMC-immunoreactive cells were located in the anterior and intermediate lobe of the pituitary gland. POMC-immunoreactive perikarya were located in the arcuate nucleus and periarcuate area. The pituitary stalk/median eminence contained sparsely distributed POMC-immunoreactive fibers, which were confined to the zona interna. POMC-immunoreactive fibers were located in the arcuate nucleus and extended rostrally from the arcuate nucleus into the telencephalon coursing adjacent to the wall of the third ventricle as well as through the anterior hypothalamus, suprachiasmatic, supraoptic nuclei and preoptic areas to the nucleus accumbens, diagonal band of Broca, olfactory tubercle, bed nucleus of the stria terminalis and the ventro-lateral aspect of the septum. Caudal projections extended along the wall of the third ventricle to the level of the mammillary bodies and also coursed dorsally, passing through the periventricular, paraventricular, and dorsal medial nuclei of the hypothalamus to the midline thalamic nuclei and habenular nucleus. Lateral projections extended from the arcuate nucleus along the dorsal aspect of the optic tract and terminated in the amygdaloid complex. The distribution of POMC-immunoreactive perikarya and fibers is similar to that of the luteinizing hormone-releasing hormone (LHRH) fiber network. Therefore the opportunities exist, anatomically, for interactions between the POMC and the LHRH systems.     

Immunocytochemical colocalization of progestin receptors and beta-endorphin or enkephalin in the hypothalamus of female guinea pigs

Double-label immunocytochemistry was used to determine whether estradiol-induced progestin receptors and either beta-endorphin or leucine-enkephalin are colocalized in female guinea pig brain. Ovariectomized, adult guinea pigs were implanted with capsules containing estradiol-17 beta to induce high levels of progestin receptors, and injected intracerebroventricularly with colchicine to improve visualization of the opiate peptides. Sections through the hypothalamus and preoptic area were processed for progestin receptor, followed by beta-endorphin or leucine-enkephalin immunocytochemistry. As reported previously, high concentrations of progestin receptor-immunoreactive (PR-IR) cells were found in the preoptic area (medial and periventricular portions, medial preoptic nucleus) and hypothalamus (anterior hypothalamic and arcuate nuclei, ventrolateral area). Many beta-endorphin-IR cells contained PR-IR in the arcuate nucleus and its surroundings (33%) and in the dorsomedial area of the hypothalamus (64%). Scattered enkephalin-IR cells were found in the septal nucleus, medial and lateral preoptic area, bed nucleus of the stria terminalis, and the arcuate nucleus. The ventromedial nucleus of the hypothalamus and dorsolateral magnocellular nucleus, respectively, contained moderate and heavy concentrations of enkephalin-IR cells. Although some of these areas also contained PR-IR, enkephalin-IR was colocalized consistently with PR-IR only in a small number of cells in the arcuate nucleus and ventromedial/ventrolateral area of the hypothalamus. These data, taken together with earlier observations that virtually all cells containing estradiol-induced PR-IR also contain estrogen receptor-IR, provide neuroanatomical evidence that hypothalamic actions of progesterone and estradiol may be mediated by beta-endorphin and/or enkephalin.     

Immunocytochemical colocalization of progestin receptors and β-endorphin or enkephalin in the hypothalamus of female guinea pigs

Double-label immunocytochemistry was used to determine whether estradiol-induced progestin receptors and either β-endorphin or leucine-enkephalin are colocalized in female guinea pig brain. Ovariectomized, adult guinea pigs were implanted with capsules containing estradiol-17β to induce high levels of progestin receptors, and injected intracerebroventricularly with co chicine to improve visualization of the opiate peptides. Sections through the hypothalamus and preoptic area were processed for progestin receptor, followed by β-endorphin or leucine-enkephalin immunocytochemistry. As reported previously, high concentrations of progestin receptor-immunoreactive (PR-IR) cells were found in the preoptic area (medial and periventricular portions, medial preoptic nucleus) and hypothalamus (anterior hypothalamic and arcuate nuclei, ventrolateral area). Many β-endorphin-IR cells contained PR-IR in the arcuate nucleus and its surroundings (33%) and in the dorsomedial area of the hypothalamus (64%). Scattered enkephalin-IR cells were found in the septal nucleus, medial and lateral preoptic area, bed nucleus of the stria terminalis, and the arcuate nucleus. The ventromedial nucleus of the hypothalamus and dorsolateral magnocellular nucleus, respectively, contained moderate and heavy concentrations of enkephalin-IR cells. Although some of these areas also contained PR-IR, enkephalin-IR was colocalized consistently with PR-IR only in a small number of cells in the arcuate nucleus and ventromedial/ventrolateral area of the hypothalamus. These data, taken together with earlier observations that virtually all cells containing estradiol-induced PR-IR also contain estrogen receptor-IR, provide neuroanatomical evidence that hypothalamic actions of progesterone and estradiol may be mediated by β-endorphin and/or enkephalin.     

Ultrastructural analysis of estrogen receptor immunoreactive neurons in the medial preoptic area of the female rat brain

Neurons of the medial preoptic area were studied in the brain of the female rat by means of ultrastructural immunocytochemistry using a monoclonal antibody generated against purified estrogen receptor (ER), in order to delineate the morphological correlates of estrogen feedback mechanisms. In addition to the preoptic area, the bed nucleus of the stria terminalis, the arcuate and ventromedial nuclei of the hypothalamus exhibited an intense labelling for estrogen receptor. At the light microscopic level, the cell nuclei were immunoreactive. No major alterations were detected in the ER expression of medial preoptic neurons sampled during the estrous cycle, but proestrous rats did exhibit a slightly increased intensity of staining. At the ultrastructural level, the ER immunoreactivity was primarily confined to the nuclei and associated with the chromatin. Long term steroid deprivation elicited by either ovariectomy or ovariectomy plus adrenalectomy resulted in a marked intensity of nuclear labelling. This pattern was not influenced by acute estradiol replacement. These morphological data indicate that neurons of the medial preoptic area have the capacity to detect estrogens via receptor mechanisms and that changes in the level of the circulating ligand are manifested in an alteration in the staining for the estrogen receptor. The study also supports the revised concept of estrogen receptor action by demonstrating the presence of receptors in the nuclei of the cells, whether or not they are occupied by their ligand.     

Hypothalamic control of visual cortical unit activity in rabbits

During the action of an extracellular polarizing current on neurons of the rabbit visual cortex electrical stimulation was applied to various hypothalamic nuclei (preoptic region, anterior hypothalamic region, lateral hypothalamus, mammillary bodies, and posterior hypothalamic nucleus). Hypothalamic stimulation was found to reduce the mean discharge frequency of most visual cortical neurons tested under conditions of anodal polarization, when the initial level of activity is considerably increased, than to a decrease in activity under conditions of cathodal polarization, when the initial level of activity is considerably reduced. The same tendency toward restoration of the initial (spontaneous) level of unit activity after hypothalamic stimulation was discovered when this level was shifted as a result of stimulation by regular flashes. The greatest effect was observed during stimulation of the preoptic region of the hypothalamus. Stimulation of the posterior hypothalamic nucleus was least effective in this respect.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 469–476, September–October, 1977.     

Immunocytochemical localization of neuropeptides in the hypothalamus of the Japanese long-fingered bat,Miniopterus schreibersii fuliginosus

Summary To elucidate the role of hypothalamic neuropeptides in regulation of reproductive phenomena of seasonally breeding feral mammals, we used Japanese long-fingered bats, Miniopterus schreibersii fuliginosus, for immunocytochemical study of distribution of the following neuropeptides in the hypothalamus: arginin vasopressin, oxytocin, luteinizing hormone-releasing hormone, somatostatin, corticotropin-releasing factor, and growth hormone-releasing factor. The size, shape and location of supraoptic, paraventricular, suprachiasmatic, and arcuate nuclei of the bat were determined. Arginin vasopressin-and oxytocin-immunoreactive magnocellular neurons were found in the supraoptic and paraventricular nuclei, where they exhibited separate distribution into two distinct groups. Parvocellular arginin vasopressin neurons occurred only in the suprachiasmatic nucleus. The hibernating bats exhibited slightly increased numbers of vasopressin and oxytocin neurons in the supraoptic and paraventricular nuclei. The pregnant bat displayed further increased numbers of vasopressin and oxytocin neurons in both nuclei. Somatostatin-immunoreactive neurons in the paraventricular nucleus were also immunopositive to anti-oxytocin serum, while those in the ventromedial and arcuate nuclei reacted solely to anti-somatostatin serum. They projected to the anterior median eminence and infundibular stalk. Luteinizing hormone-releasing hormone-immunoreactive perikarya were scattered throughout the basal hypothalamus, being particularly abundant in the arcuate nucleus. They were larger in size in hibernating bats than those in normal (non-pregnant) and pregnant females. They projected fibers mainly to the internal layer of the median eminence and infundibular stalk. A few luteinizing hormone-releasing hormone-reactive fibers were also observed in the organum vasculosum laminae terminalis, lateral habenular nuclei, pineal stalk, retroflexus fasciculus, and olfactory tubercle. Corticotropin releasing factor-immunoreactive perikarya were distributed in the paraventricular nucleus and medial preoptic area and projected into the external layer of the anterior median eminence, while growth hormone-releasing factor-immunoreactive perikarya occurred only in the arcuate nucleus and projected into the posterior part of the median eminence.     

Lateral septal projections onto tubero-infundibular neurons in the hypothalamus of the guinea pig

Efferent projections of the lateral septal nucleus (LS) to the preoptic area and the hypothalamus were identified in 20 female guinea pigs after iontophoretic injection of the anterograde axonal tracer Fluoro-Ruby. Tubero-infundibular (TI) neurons of the preoptic area and the hypothalamus were retrogradely labeled after intracardiac injection of Granular Blue or Fluoro-Gold. Magnocellular neurons of the supraoptic and paraventricular nuclei were also labeled. The double labeling procedure allowed an estimation of the extent of the direct relationship between LS efferents and TI neurons. Contacts between lateral septal fibers and TI cell bodies were mainly observed at the light-microscopical level in the preoptic area. A group of labeled fibers coursing along the third ventricle established sparse connections with hypothalamic periventricular TI neurons. A few appositions was observed in the infundibular (arcuate) nucleus, suggestive of a monosynaptic regulation of TI neurons by a septo-arcuate tract. Close association with labeled magnocellular neurons was also noted at the edge of the supraoptic and paraventricular nuclei. The sparse but direct connections between LS and TI neurons may be involved in the neuroendocrine functions of the LS.     

Quantitative protein changes in the hypothalamic neurons of pubertal male rats, castrated neonatally.

The effect of neonatal castration of male rats on the sexual differentiation of the hypothalamus at puberty was studied. Male rats were castrated on days 1, 5 and 7 after birth. Their brains were processed for study on days 83-85. The neurons and cell nuclei of the preoptic area, mediobasal and ventromedial nuclei were assessed for changes in cell and nuclear sizes and dry weight (calculated using interferometric methods). Neonatal castration resulted in size as well as dry weight increase in the neurons of the anterior and mediobasal hypothalamus. The dry weight increased by 34% (P less than 0.001) in the medial preoptic area, by 25% (P less than 0.001) in the arcuate neurons and by 22% (P less than 0.001) in the ventromedial nucleus. The cell nuclei exhibited perceptible weight increase too--in the medial preoptic area 68% (P less than 0.001); 55% in the arcuate neurons (P less than 0.001), and 39% in the ventromedial region. The weight and size increases in neonatally castrated males were equal to those of females of the same age. In rats castrated on day 7, the cell sizes and dry weights of the ventromedial nucleus increased but the cell nuclei exhibited only little change. It is assumed that the changes in the dry weight may be the result of increased synthetic processes in these groups of neurons which are connected with the tonic and cyclic release of gonadotropins. These changes also point to the hypothalamic differentiation shifting to the female type in the absence of the inducing effect of androgens.     

Responses of limbic cortical neurons to stimulation of splanchnic and sciatic nerves and of the mammillary bodies

Spontaneous and evoked unit activity in the anterior limbic cortex in response to stimulation of the splanchnic and sciatic nerves and of the mammillary region of the hypothalamus were recorded extracellularly in acute experiments on cats. The study of heterogeneous transsynaptic influence on limbic cortical neurons showed that in the presence of effective sensory viscerosomatic convergence, weak convergence of influences from the central hypothalamic and peripheral sources took place. Short-latency responses of limbic cortical neurons to stimulation of the mammillary bodies consisted of orthodromic and antidromic responses, evidence of the existence of short two-way connections between the anterior limbic cortex and mammillary nuclei of the hypothalamus.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 419–426, September–October, 1979.     

Estrogen receptor and progesterone receptor-immunoreactive cells are not co-localized with gonadotropin-releasing hormone in the brain of the female mink (Mustela vison)

The distribution of gonadal steroid (estrogen, progesterone) receptors in the brain of the adult female mink was mapped by immunocytochemistry. Using a monoclonal rat antibody raised against human estrogen receptor (ER), the most dense collections of ER-immunoreactive (IR) cells were found in the preoptic/anterior hypothalamic area, the mediobasal hypothalamus (arcuate and ventromedial nuclei), and the limbic nuclei (amygdala, bed nucleus of the stria terminalis, lateral septum). Immunoreactivity was mainly observed in the cell nucleus and a marked heterogeneity of staining appeared from one region to another. A monoclonal mouse antibody raised against rabbit uterine progesterone receptor (PR) was used to identify the PR-IR cells in the preoptic/anterior hypothalamic area and the mediobasal hypothalamus (arcuate and ventromedial nuclei). This study also focused on the relationship between cells containing sex-steroid receptors and gonadotropin-releasing hormone (GnRH) neurons on the same sections of the mink brain using a sequential double-staining immunocytochemistry procedure. Although preoptic and hypothalamic GnRH neurons were frequently in close proximity to perikarya containing ER or PR, they did not themselves possess receptor immunoreactivity. The present study provides neuroanatomical evidence that GnRH cells are not the major direct targets for gonadal steroids and confirms for the first time in mustelids the results previously obtained in other mammalian species.     

The distribution of luteinizing hormone-releasing hormone (LHRH) neurons and fibers in the Formosan rock-monkey

The anatomical distribution of neurons and fibers containing Luteinizing Hormone Releasing Hormone-Immunoreactivity (LHRH-IR) in the brain of the Formosan Rock-Monkey was investigated employing immunohistochemical techniques. LHRH-IR neurons were observed in an area demarcated rostrally by the diagonal band of Broca and caudally by the mammillary area. The majority of these neurons were principally localized in the preoptic area, periventricular zone, and the arcuate nucleus. The supraoptic nucleus, septal area, triangular septal nucleus, nucleus of the diagonal band of Broca, suprachiasmatic nucleus, retrochiasmatic area, mammillary area, and the amygdala also exhibited neuronal LHRH immunoreactivity. LHRH-IR fibers appeared to originate in all of the above areas of the hypothalamus, project caudally, and subsequently terminate in the median eminence (ME). In addition to the above, LHRH-IR fibers were also detected in the organum vasculosum of the lamina terminalis (OVLT). A scattering of LHRH-IR fibers were also observed in several extrahypothalamic regions, notably the subfornical organ, indusium griseum, habenular complex, septohypothalamic nucleus, and amygdala.     

Neuronal inputs from the hypothalamus and brain stem to the medial preoptic area of the ram: neurochemical correlates and comparison to the ewe

The retrograde tracer, FluoroGold, was used to trace the neuronal inputs from the septum, hypothalamus, and brain stem to the region of the GnRH neurons in the rostral preoptic area of the ram and to compare these imputs with those in the ewe. Sex differences were found in the number of retrogradely labeled cells in the dorsomedial and ventromedial nuclei. Retrogradely labeled cells were also observed in the lateral septum, preoptic area, organum vasculosum of the lamina terminalis, bed nucleus of the stria terminalis, stria terminalis, subfornical organ, periventricular nucleus, anterior hypothalamic area, lateral hypothalamus, arcuate nucleus, and posterior hypothalamus. These sex differences may partially explain sex differences in how GnRH secretion is regulated. Fluorescence immunohistochemistry was used to determine the neurochemical identity of some of these cells in the ram. Very few tyrosine hydroxylase-containing neurons in the A14 group (<1%), ACTH-containing neurons (<1%), and neuropeptide Y-containing neurons (1-5%) in the arcuate nucleus contained FluoroGold. The ventrolateral medulla and parabrachial nucleus contained the main populations of FluoroGold-containing neurons in the brain stem. Retrogradely labeled neurons were also observed in the nucleus of the solitary tract, dorsal raphe nucleus, and periaqueductal gray matter. Virtually all FluoroGold-containing cells in the ventrolateral medulla and about half of these cells in the nucleus of the solitary tract also stained for dopamine beta-hydroxylase. No other retrogradely labeled cells in the brain stem were noradrenergic. Although dopamine, beta-endorphin, and neuropeptide Y have been implicated in the regulation of GnRH secretion in males, it is unlikely that these neurotransmitters regulate GnRH secretion via direct inputs to GnRH neurons.     

Ultrastructural analysis of estrogen receptor immunoreactive neurons in the medial preoptic area of the female rat brain

Summary Neurons of the medial preoptic area were studied in the brain of the female rat by means of ultrastructural immunocytochemistry using a monoclonal antibody generated against purified estrogen receptor (ER), in order to delineate the morphological correlates of estrogen feedback mechanisms. In addition to the preoptic area, the bed nucleus of the stria terminalis, the arcuate and ventromedial nuclei of the hypothalamus exhibited an intense labelling for estrogen receptor. At the light microscopic level, the cell nuclei were immunoreactive. No major alterations were detected in the ER expression of medial preoptic neurons sampled during the estrous cycle, but proestrous rats did exhibit a slightly increased intensity of staining. At the ultrastructural level, the ER immunoreactivity was primarily confined to the nuclei and associated with the chromatin. Long term steroid deprivation elicited by either ovariectomy or ovariectomy plus adrenalectomy resulted in a marked intensity of nuclear labelling. This pattern was not influenced by acute estradiol replacement.These morphological data indicate that neurons of the medial preoptic area have the capacity to detect estrogens via receptor mechanisms and that changes in the level of the circulating ligand are manifested in an alteration in the staining for the estrogen receptor. The study also supports the revised concept of estrogen receptor action by demonstrating the presence of receptors in the nuclei of the cells, whether or not they are occupied by their ligand.Supported by grants from the IBRO/MacArthur Foundation Network Grant, the National Science Foundation (NSF INT 8703030), the Hungarian Academy of Sciences (OTKA 104), the National Institutes of Health (NS 19266), the National Foundation of Technical Development (OKKFT Tt 286/1986) and the Well-come Trust (14685/1.5)     

The efferent connections of the lateral septal nucleus in the guinea pig: projections to the diencephalon and brainstem

Summary The anterograde Phaseolus vulgaris-leucoagglutinin (PHA-L) tracing technique was used to determine the distribution of efferent fibers originating in the lateral septal nucleus of the guinea pig. For complementary detection of the chemical identity of the target neurons, double-labeling immunocytochemistry was performed with antibodies to PHA-L and to vasopressin, oxytocin, vasoactive intestinal polypeptide, serotonin or dopamine -hydroxylase, respectively. The hypothalamus received the majority of the PHA-L-stained septofugal fibers. Here, a specific topography was observed. (1) The medial and lateral preoptic area, (2) the anterior, lateral, dorsal, posterior hypothalamic and retrochiasmatic area, (3) the supraoptic, paraventricular, suprachiasmatic, dorsomedial, caudal ventromedial and arcuate nuclei, and (4) the tuberomammillary, medial and lateral supramammillary, dorsal and ventral premammillary nuclei always contained PHA-L-labeled fibers. The rostral portion of the ventromedial nucleus and the medial and lateral mammillary nucleus only occasionally showed weak terminal labeling. In other diencephalic areas, termination of PHA-L-labeled fibers was observed in the epithalamus and the nuclei of the midline region of the thalamus. In the mesencephalon, terminal varicosities occurred in the ventral tegmental area, interfascicular and interpeduncular nucleus, and periaqueductal gray. In addition, the dorsal and medial raphe nuclei of the metencephalon, together with the locus coeruleus and the dorsal tegmental nucleus, received lateral septal efferents.     

Electrophysiological analysis of corticofugal influences on preoptic neurons

Evoked potential (EPs) and responses of the medial (MPO) and lateral (LPO) preoptic region (RPO) and adjacent structures of the hypothalamus to stimulation of the prefrontal (area 8) and cingulate (area 24) cortex, piriform lobe (periamygdaloid cortex), and hippocampus (area CA3) were investigated in acute experiments on cats under ketamine anesthesia. The most pronounced EPs were observed in the RPO after stimulating the piriform and cingulate cortex. A close relation was found between neuronal responses and EP components. The majority of neurons responding to stimulation of various cortical structures were localized in the LPO, where primarily excitatory responses dominate. The MPO contained somewhat fewer neurons responding to cortical stimulation, and the dominant response here was primarily inhibitory. The ratio of inhibitory and excitatory responses in the LPO was 0.6:1 and in the MPO 5.8:1. Primarily in-inhibitory responses dominated also in the LPO zone adjacent to the bed nucleus stria terminalis (BST) and primarily excitatory in the region surrounding the supraoptic nucleus (SO) (respective ratios 4.9:1 and 0.7:1). The RPO is a broad convergence zone, where 3/4 of the neurons responded to stimuli of two and more cortical regions.A. M. Gorky Medical Institute, Ukrainian Minstry of Health, Donetsk. Translated from Neirofiziologiya, Vol. 23, No. 6, pp. 709–719, November–December, 1991.     

A fluorescence microscopic study of the distribution of monoamines in the hypothalamus of the cat

Three distinct groups of monoamine (MA)-containing nerve cell bodies have been visualized in the hypothalamus and preoptic area of the cat by means of the Falck-Hillarp fluorescence histochemical technique. First, numerous small-sized catecholamine (CA) type neurons were disclosed within the ventral half of the periventricular area in the supraoptic and middle hypothalamic regions. The round to oval neurons of this medio-ventral group were more especially abundant around the base of the third ventricle, within the arcuate and supraopticus diffusus nuclei. Numerous medium-sized CA perikarya identified as the dorsal group, were also mapped out in the dorsal and posterior hypothalamic areas. Finally, a small population of both CA and serotonin (5-hydroxytryptamine, 5-HT)-containing neurons was disclosed within the lateral area of the middle and mammillary hypothalamic regions. These multipolar or elongated neurons which compose the lateral group were lying either along the ventrolateral surface of the hypothalamus or around the ventrolateral aspect of the fornix. In addition to these three MA cell groups, a few cells displaying a fluorescence of the CA type were also visualized in the so-called “dorsal chiasmatic nucleus” after α-methyl-dopa treatment. High density of CA axon terminals were found, on the other hand, in the external layer of the median eminence, in the dorsomedial, paraventricular, supraoptic and suprachiasmatic nuclei, and also within nucleus interstitialis of stria terminalis. In the present study, however, it was not possible to identify with certainty any concentration of 5-HT axon terminals in the cat hypothalamus. Therefore, except for the lateral cell group which could be peculiar to the cat, the topographical distribution of MA nerve cell bodies and axon terminals in the hypothalamus of the cat appears similar to the morphological organization of the MA neuronal elements in the hypothalamus of the rat.     

Natural variation in paternal behavior is associated with central estrogen receptor alpha and oxytocin levels

In monogamous mammals paternal care plays an important role in the neural and behavioral development of offspring. However, the neuroendocrine mechanisms underlying paternal behavior remain poorly understood. Here, we investigate the association between natural variation in paternal responsiveness and central levels of oxytocin (OT) and estrogen receptor alpha (ERα). We used the frequency of licking and grooming behavior to distinguish low paternal responsiveness and high paternal responsiveness in virgin mandarin voles (Microtus mandarinus). Males that engaged in high paternal behavior had elevated levels of OT immunoreactive neurons in the paraventricular nuclei of the hypothalamus and supraoptic nuclei of the hypothalamus compared with males that displayed low paternal behavior. Likewise, males of high paternal responsiveness had more ERα immunoreactive neurons in the medial preoptic area, bed nucleus of the stria terminalis, arcuate nucleus of the hypothalamus and medial amygdaloid nucleus compared to low responsive males. The level of ERα immunoreactive neurons in the ventromedial hypothalamic nucleus was lower in highly paternal males compared to less paternal males. These results suggest that natural variation in paternal responsiveness may be directly related to variation in central OT and ERα.