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PubMed1994

[Effects of arterial blood pressure change on release of GABA in the posterior hypothalamus conscious of freely moving rats].

Push-pull superfusion technique was used to investigate the release of endogenous gamma-aminobutyric acid (GABA) in the posterior hypothalamus of the conscious, freely moving rat in response to peripherally applied drugs or experimentally induced blood pressure changes. The rise in blood pressure elicited by intravenous infusion of phenylephrine (15 micrograms.kg-1.min-1) or blood (3 ml/100 g) was associated with an increased rate of GABA release in the posterior hypothalamus. Hypotension produced by nitroprusside (30 micrograms.kg-1.min-1), chlorisondamine (3 mg.kg-1,iv) and controlled bleeding (3 ml/100 g) led to a counteracting decrease in hypothalamic GABA outflow. This finding suggests that GABAergic neurons of the conscious, freely moving rat in the posterior hypothalamus are involved in cardiovascular control and possess a hypotensive function.

Animals↗
PubMed1994

Ontogeny of immunocytochemically demonstrable androgen- and androgen receptor-containing cells in the hypothalamus and adenohypophysis of the chick embryo.

Brain sections of male chick embryos, 6.5-18.5 days of age, were examined immunocytochemically for the presence of androgen- and androgen receptor-containing cells in the hypothalamus and adenohypophyseal pars distalis. Using antibodies (Ab) against both androgens (T-Ab) and the androgen receptor (AR-Ab), single- and double-immunostained cells were located in a total of five nuclei of the anterior-, mid-, and posterior-hypothalamus, as well as in the rostral and caudal lobes of the adenohypophyseal pars distalis. From Days 9.5-12.5, the mean number of androgen-immunostained cells within the hypothalamus and pars distalis increased significantly (P < 0.01), while from Days 12.5-18.5 there was no further statistically significant increase. The results of the present investigation support previous findings which suggest that in the chick embryo the negative feedback loop of the hypothalamo-adenohypophyseal-testicular (HATest) axis is functional by the 13th day of development (Woods et al., 1989a,b). They also agree with the observations of Wilson and Glick (1970) that in the male chick embryo testosterone organizes masculine mating behavior prior to Day 13.0.

Androgens↗
PubMed1993

Interleukin-1 beta augments release of norepinephrine, dopamine, and serotonin in the rat anterior hypothalamus.

We investigated the effects of interleukin-1 beta (IL-1 beta), administered directly into the rat anterior hypothalamus (AHY), on monoamine release in the same region by using a brain microdialysis technique and an HPLC-electrochemical detection system. First, to study the local effects of IL-1 beta, we used a microdialysis probe equipped with a microinjection tube for administering IL-1 beta in the same region into which the probe had been inserted. IL-1 beta (1 ng) injected directly into the AHY elicited release of norepinephrine (NE), dopamine (DA), and 5-HT, as well as increases in their metabolites, 4-hydroxy-3-methoxyphenylglycol, 3,4-dihydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenylacetic acid, and 5-hydroxyindole-3-acetic acid, in the AHY. Vehicle alone exerted no effect on monoamine release. Although the elevated levels of NE and DA persisted for more than 6 hr after injection of IL-1 beta, the elevated levels of 5-HT were transient. Second, in order to investigate whether this effect of IL-1 beta is a direct action in the AHY, we performed in vitro experiments using hypothalamus slices. IL-1 beta (0.1 and 1 nM) increased the levels of each monoamine released from hypothalamic slices in a dose-dependent manner. These findings suggest that IL-1 beta acts directly on the hypothalamus to induce release of NE, DA, and 5-HT. Third, the roles of prostaglandins (PGs) in NE release in the AHY elicited by direct injection of IL-1 beta were examined.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1996

Regulation of progesterone receptor gene expression by sex steroid hormones in the hypothalamus and the cerebral cortex of the rabbit.

The effects of estradiol benzoate (EB) and progesterone (P4) upon progesterone receptor (PR) gene expression in the cerebral cortex and the hypothalamus of the rabbit were studied. Ovariectomized adult rabbits were subcutaneously treated with EB (25 micrograms/kg) for 2 days, and with EB (25 micrograms/kg) + a single dose of P4 (5 mg/kg) on day 3. Twenty-four hours after the last dose, the frontal cortex, the hypothalamus and the uterus were excised, total RNA was extracted and processed for reverse transcription-polymerase chain reaction. PR gene expression was induced by EB and down-regulated by P4 both in the frontal cortex and the hypothalamus in a manner similar to that observed in the uterus. The finding that PR gene transcription is regulated by steroid hormones in the cerebral cortex suggests that post-transcriptional processes are involved in the insensitivity of cortical PR protein to steroids regulation previously reported with binding techniques.

Animals↗
PubMed1996

Macroscopic blood supply to the hypophysis and hypothalamus of the ostrich (Struthio camelus).

The branching pattern of the Aa. carotes internae and the macroscopic blood supply to the hypophysis and hypothalamus of the ostrich were studied on ten dissected acrylic vascular-injected heads and ten corrosion preparations of acrylic vascular casts of the head. The A. carotis cerebralis was found to be the only source of blood supply to the hypophysis and hypothalamus. The neurohypophysis was supplied by the caudal hypophyseal and infundibular arteries. The pars distalis was supplied by portal vessels from the ventral hypothalamic region, and it also received arterial blood directly from the infundibular arteries. The hypothalamus received blood from the Aa. infundibulares. A. ventralis tecti mesencephali and A. preopticae.

Animals↗
PubMedDate not supplied

[Effect of estradiol on content of monoamines and acetylcholine in rat hypothalamus].

Administration of estradiol-benzoate in a dose of 0.5 Mg for 4 days causes a twice increase in the content of acetylcholine in hypothalamus of impuberal female rats and statistically significant decrease in the content of GABA. The level of serotonin, dopamine, noradrenaline and histamine in the hypothalamus of the animals is not affected by 0.5 Mg of estradiol-benzoate. Administration of prolactin against a background of estradiol--benzoate normalizes the content of GABA and produces a statistically significantly drop in the level of acetylcholine in the hypothalamus. A conclusion is drawn that acetylcholine and GABA are involved into regulation of prolactin secretion in rats.

Acetylcholine↗
PubMed1997

PSA-NCAM and B-50/GAP-43 are coexpressed by specific neuronal systems of the adult rat mediobasal hypothalamus that exhibit remarkable capacities for morphological plasticity.

The present study was designed to determine whether the mediobasal hypothalamus of adult rats contains neurons that continue to coexpress the highly polysialylated neural cell adhesion molecule (PSA-NCAM) and B-50/GAP-43, two proteins coexpressed by virtually all of the neurons of the fetal and neonatal rat central nervous system. Confocal laser scanning microscopy combined with double- or triple-fluorescence immunostaining was used to identify the hypothalamic neurons that express high levels of both PSA-NCAM and B-50/GAP-43 and to study the possible modifications of their morphological organization following a surgical lesion through the mediobasal hypothalamus. In intact animals, PSA-NCAM and B-50/GAP-43 were found to be colocalized within numerous fibers projecting throughout the external layer of the median eminence that were immunoreactive for either gamma-aminobutyric acid (GABA) or tyrosine hydroxylase (TH). Three to 30 days after a lesion through this region, numerous regenerating axonal sprouts, triple-immunostained for PSA-NCAM, B-50/GAP-43, and either GABA or TH, were detected along the ventricular surface of, and throughout the perivascular layer of, the median eminence. Surprisingly, high levels of PSA-NCAM and B-50/GAP-43 were also associated with numerous supraependymal neurons that exhibited long ramified processes and were immunoreactive for GABA but TH-negative. The use of the proliferation marker, 3H-thymidine, further indicated that the emergence of such supraependymal neurons after median eminence lesion was not related to the proliferation of preexisting quiescent cells. These data indicate that the mediobasal hypothalamus of the adult rat contains two neuronal systems, in which the continued coexpression of PSA-NCAM and B-50/GAP-43 is related to remarkable capacities for postlesional, morphological plasticity.

Animals↗
PubMedDate not supplied

[Effect of isolation of the mediobasal hypothalamus on the predatory aggressiveness of rats].

A study was made of the influence of isolation of the medio-basal hypothalamus area on the predatory aggression of albino male rats, which was measured by the test of mouse-killing. In three weeks after the operation the aggressiveness of rats increased eightfold. Partial isolations--anterior, long-posterior and posterior--did not change the killing aggression of the rats. Extension of dimensions of complete isolation up to the lateral hypothalamic area did not lead to the appearance of "mice killers" among the experimental rats. A conclusion has been drawn that the medio-basal hypothalamus has an inhibitory effect on the predatory aggression, which is achieved in multiple ways and is directed at the lateral hypothalamus.

Animals↗
PubMed1998

An alternate pathway for visual signal integration into the hypothalamo-pituitary axis: retinorecipient intergeniculate neurons project to various regions of the hypothalamus and innervate neuroendocrine cells including those producing dopamine.

Using tract tracing and immunocytochemistry, this study explored the connectivity between lateral geniculate efferents and neurons of the hypothalamus, including those producing dopamine, that have direct access to fenestrated capillaries. It was also determined whether the intergeniculate neurons that give rise to hypothalamic projections are targeted by retinal axons. Within the hypothalamus, Phaseolus vulgaris leucoagglutinin-labeled, lateral geniculate efferents were observed in the suprachiasmatic nucleus, subparaventricular area, periventricular nuclei, medial preoptic areas, and between the arcuate and ventromedial nuclei. In these sites, intergeniculate efferents contacted populations of neurons that were retrogradely labeled from fenestrated capillaries by the intraperitoneal injection of fluorogold. Hypothalamic dopamine neurons, a population of which was neuroendocrine, were also synaptic targets of lateral geniculate efferents. After injection of the retrograde tracer fluorogold into these hypothalamic projection sites in parallel with bilateral enucleation, retrogradely labeled perikarya were restricted to the intergeniculate leaflet. All of the labeled perikarya contained infolded nuclei, and their distal dendrites were frequently found to be contacted by degenerated, retinal fibers. This study provides morphological evidence for a signaling pathway from the retina through the intergeniculate leaflet to hypothalamic cells that participate in neuroendocrine regulations. These observations raise the possibility that visual signals independent of the circadian clock may also influence the hypothalamo-pituitary axis. In light of the overlapping distribution of intergeniculate and suprachiasmatic efferents in the hypothalamus and their similar relationship with neuroendocrine cells, it is suggested that integration of circadian and visual signals can occur outside of the suprachiasmatic nucleus to regulate endocrine rhythms.

Animals↗
PubMed1998

Chemically defined projections linking the mediobasal hypothalamus and the lateral hypothalamic area.

Recent studies have identified several neuropeptide systems in the hypothalamus that are critical in the regulation of body weight. The lateral hypothalamic area (LHA) has long been considered essential in regulating food intake and body weight. Two neuropeptides, melanin-concentrating hormone (MCH) and the orexins (ORX), are localized in the LHA and provide diffuse innervation of the neuraxis, including monosynaptic projections to the cerebral cortex and autonomic preganglionic neurons. Therefore, MCH and ORX neurons may regulate both cognitive and autonomic aspects of food intake and body weight regulation. The arcuate nucleus also is critical in the regulation of body weight, because it contains neurons that express leptin receptors, neuropeptide Y (NPY), alpha-melanin-stimulating hormone (alpha-MSH), and agouti-related peptide (AgRP). In this study, we examined the relationships of these peptidergic systems by using dual-label immunohistochemistry or in situ hybridization in rat, mouse, and human brains. In the normal rat, mouse, and human brain, ORX and MCH neurons make up segregated populations. In addition, we found that AgRP- and NPY-immunoreactive neurons are present in the medial division of the human arcuate nucleus, whereas alpha-MSH-immunoreactive neurons are found in the lateral arcuate nucleus. In humans, AgRP projections were widespread in the hypothalamus, but they were especially dense in the paraventricular nucleus and the perifornical area. Moreover, in both rat and human, MCH and ORX neurons receive innervation from NPY-, AgRP-, and alpha-MSH-immunoreactive fibers. Projections from populations of leptin-responsive neurons in the mediobasal hypothalamus to MCH and ORX cells in the LHA may link peripheral metabolic cues with the cortical mantle and may play a critical role in the regulation of feeding behavior and body weight.

Agouti-Related Protein↗
PubMed1985

Surgical anatomy of the hypothalamus.

Described are the borderlines of the hypothalamus, its nuclei and fiber connections and its functions. The vascular supply of the hypothalamic area is included. Furthermore measurements of the IIIrd ventricle and distances between surface areas of the brain and skull as well as different landmarks near the hypothalamus are presented. For example the distance between the frontal pole and the lamina terminalis in our material measures 59.3 (52-65) mm. Distances for the different approaches to the hypophyseal region (transsphenoideal, pterional, supra- and infratentorial, transcallosal and transventricular) are also given.

Body Temperature Regulation↗
PubMed1985

An autoradiographic analysis of the time of origin of neurons in the hypothalamus of the cat.

The pattern of neurogenesis of the cat hypothalamus was studied by the use of the [3H]thymidine autoradiographic method. The neurons of the cat hypothalamus are nearly all generated in a period from embryonic days E21 to E35, and in most cases the neurons in a single nucleus are generated over a much shorter period. The dominant gradient along which the cells are organized is lateral-medial (outside-in). This gradient was apparent in all nuclei except the periventricular and arcuate nuclei. Two other gradients were observed in some, but not all, nuclei. These were along the dorsoventral and the posteroanterior axis. The dorsoventral gradient was uniformly less pronounced than the lateromedial gradient. The posteroanterior gradient was most obvious in the mammillary complex. An analysis of the data suggests that the neurons of individual nuclei do not necessarily have a unique production history. This suggests that insofar as nuclear formation is concerned, factors such as the parental population generating the neurons that populate a nucleus, as well as the early neuronal interconnections, may play a more important role than the birthdates themselves.

Animals↗
PubMed1976

Sterilization of female rats by neonatal placement of estradiol micropellets in anterior hypothalamus.

A pair of micropellets of a 1% or 10% estradiol (E2)-paraffin mixture (containing 0.2 or 2 mug E2, respectively) or paraffin alone were implanted subcutaneously or intracerebrally in 5-day-old female rats. Animals given 10% E2 pellets became sterilized regardless of loci of the pellets. Of those which had received 1% E2 pellets, only animals with micropellets in the anterior hypothalamus became sterilized. It is suggested that neuronal components which are affected irreversibly by neonatal estrogen treatment are localized in the anterior hypothalamus.

Animals↗
PubMed1980

The stereotaxic configuration of hypothalamus nerve centres in the pig.

The purpose of this work was to state the three-dimensional position of the nuclei of the hypothalamus of the pig. The examinations were made on 12 brains of the pigs weighing from 95 to 105 kg. The length of the skulls in the studied animals varied between 26.5 to 28 cm. We have taken the following stereotaxic zero planes: 1. a horizontal plane joining the interaurical line and the upper edges of eye-sockets; 2. a transversal plane runs across the interaurical line vertically to the horizontal plane; 3. a sagittal plane corresponds to the plane of symetry of brain. The brains were fixed with 10% neutralized formalin, dehydrated in ethyl alcohol, embeded in paraffin and cut in three planes into sections 15 micrometers thick; sections were stained by method of Klüver and Barrera. The examinations of the histological preparations thus obtained furnished data for describing the position of the hypothalamus nuclei in the pig.

Animals↗
PubMed1984

Distribution of immunoreactive substance P neurons in the hypothalamus and pituitary of the rhesus monkey.

The distribution of immunoreactive substance P (IR-SP) neurons was examined in the hypothalamus and pituitary gland of the rhesus monkey by using the peroxidase-antiperoxidase immunocytochemical technique. Immunoreactive SP cell bodies were observed in the arcuate nucleus, in the region lateral to the arcuate nucleus, and in the median eminence (ME). Immunoreactive SP cells were also seen in the periventricular area of the dorsal tuberal region. A rich network of SP fibers was concentrated in the arcuate region, and the fiber stain was particularly dense in the external zone of the median eminence and in the external layer of the infundibular stalk. Also, substance P fibers were seen in the internal layer of the pituitary stalk and in the neural lobe of the pituitary gland. Outside the hypothalamus a dense network of IR-SP fibers was observed in the globus pallidus.

Animals↗
PubMed1976

Tuberoinfundibular neurons in the basomedial hypothalamus of the rat: electrophysiological evidence for axon collaterals to hypothalamic and extrahypothalamic areas.

In pentobarbital or urethane anesthetized rats, the activity of 889 mediobasal hypothalamic neurons was studied for evidence of a response to median eminence stimulation. Evidence of antidromic invasion, which indicated a projection to the median eminence, identified 134 cells (15%) as 'tuberoinfundibular' neurons. Antidromic spike latencies ranged from 0.5 to 14.0 msec (4.3 +/- 2.9 S.D.); conduction velocities were under 1.0 m/sec and were generally slower for tuberoinfundibular neurons located closest to the ventral surface of the hypothalamus. Certain tuberoinfundibular neurons followed paired median eminence shocks at frequencies up to 500 Hz; an increase in both the threshold and the latency for the second antidromic spike was observed with interstimulus intervals under 4 msec. Only 38% of tuberoinfundibular neurons were spontaneously active; 24 of 29 spontaneously active neurons displayed evidence of recurrent inhibition with durations up to 150 msec and at latencies which approximated that of the antidromic spike but which did not depend upon antidromic invasion. Similar responses were observed from 33 spontaneously active non-tuberoinfundibular neurons. Evidence of orthodromic excitation in response to median eminence shocks was observed from 22 other medial hypothalamic neurons. Latencies for excitation ranged from 1.5 to 9.0 msec (mean 4.5 +/- 2.1 S.D.). Simultaneous antidromic invasion from other hypothalamic and extrahypothalamic sites was observed from 8 tuberoinfundibular neurons. These sites included the anterior hypothalamic area (2 cells), the preoptic area (3 cells) and the thalamic nucleus medialis dorsalis (3 cells). These results indicate the presence of axon collaterals within the tuberoinfundibular system; some appear to terminate locally within the hypothalamus, while others extend rostrally and dorsally into extrahypothalamic areas. These connections may provide pathways for extrahypothalamic distribution of peptides which regulate adenohypophyseal secretion, and suggest that these peptides may subserve alternate regulatory roles within the central nervous system.

Action Potentials↗
PubMed1982

Molecular-weight profiles of immunoreactive corticotropin in the hypothalamus of the aging rat.

Extracts of the medial basal hypothalamus (MBH), the preoptic anterior hypothalamus (POA), or the pituitary gland of young (4-month-old) and old (18-month-old) female rats were fractionated on columns of Sephadex G-75 superfine. Five forms of immunoreactive corticotropin (ACTHi) were found in the MBH or POA: greater than 40K, 30-40K, 20-30K, 5.7K, and 4.5K. In contrast, 4 forms of ACTHi were found in the pituitary gland: 30-40K, 20-30K, 5.7K, and 4.5K. Thus, hypothalamic tissue contains a large form of ACTH (greater than 40K ACTH) which is not present in the pituitary gland. We tentatively identified greater than 40K ACTH as a large form of pro-opiocortin, 30-40K ACTH as pro-opiocortin, 20-30K ACTH as ACTH biosynthetic intermediate, 5.7K ACTH as glycosylated ACTH 1-39, and 4.5K ACTH as ACTH 1-39. The content of ACTHi in the MBH and POA of old rats was lower than that of young rats. Nevertheless, regardless of the age of the animals, the fractional amount of 30-40K ACTHi was high in the MBH (a region that includes the presumed site of biosynthesis of pro-opiocortin) compared to that in the POA (a region that is distant to the site of biosynthesis of pro-opiocortin). Moreover, the reduced fractional amount of 30-40K ACTHi in the POA was associated with an increased fractional amount of greater than 40K, 20-30K, 5.7K, and 4.5K ACTHi. These findings are consistent with a precursor-product relationship between the 30-40K ACTHi and 20-30K ACTHi, 5.7K ACTHi, and 4.5K ACTHi.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1986

GRF neurons in the rat hypothalamus.

The growth hormone-releasing factor (GRF)-containing neuronal system was immunohistochemically studied in the rat hypothalamus. The immunolabeled cell bodies were determined by intraventricular administration of colchicine 24 h before killing. In intact animals, the neurons appeared in the ventral portion of the arcuate nucleus (group 1) and in the area surrounding the ventromedial nucleus (group 2). Most of the cell bodies also indicated immunoreactivity for tyrosine hydroxylase (TH). The immunoreactive fibers accumulated showing a palisade arrangement in the external layer of the median eminence. The rats treated neonatally with monosodium glutamate revealed group 2 neurons and a few immunoreactive fibers in the median eminence. Half-anterolateral deafferentation of the medial basal hypothalamus, which was performed to isolate group 1 neurons or both group 1 and 2 neurons from the other brain parts, did not remarkably affect the appearance of the fibers in the median eminence. However, the perikarya were hypertrophic and strongly immunolabeled for GRF and TH. It is concluded that the fibers containing GRF in the median eminence derive mostly from group 1 neurons, and that the neurons may be regulated by an inhibitory mechanism by other neurons on the outside of the deafferented hypothalamic islands. GRF synthesized in group 2 neurons may act on other neurons as a neurotransmitter-like substance.

Animals↗