Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HYPOTHALAMUS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1982

A 14C-2-deoxyglucose analysis of the neural pathways of the limbic forebrain in the rat: II. The hypothalamus.

An attempt was made to characterize the nature of the functional organization of the hypothalamus by observing the patterns of uptake of 14C-2-deoxyglucose (2DG) following electrical stimulation of different regions within the preoptico-hypothalamus in the rat. The experimental paradigm consisted of electrical brain stimulation delivered continuously for periods of 30 sec on and 30 sec off for 45 minutes following injection of 2DG. Brains were removed and processed for autoradiography. Activation of the medial forebrain bundle was noted following stimulation of the nucleus accumbens and lateral preoptico-hypothalamus. Activated fibers could be followed only in a caudal direction through the medial forebrain bundle and into the ventral tegmental area as a result of nucleus accumbens stimulation. Stimulation of the lateral preoptic region or of the anterior half of lateral hypothalamus produced activation of the lateral septal nucleus, lateral habenular nucleus, perifornical region, midline thalamus and ventral tegmental area. Since stimulation of the perifornical hypothalamus significantly activated the rostro-caudal extent of the midbrain cental gray, it is suggested that impulses from the lateral hypothalamus reach the lower brainstem via its connections with the perifornical hypothalamus. Ventromedial hypothalamic stimulation activated only the lateral septal nucleus, cortico-medial amygdala and medial preoptico-hypothalamus, while medial preoptico-hypothalamic stimulation resulted in increased 2DG uptake in the midbrain central gray, thus suggesting that medial hypothalamic impulses reach the brainstem by first ascending to the level of the preoptico-hypothalamus. Mammillary body stimulation orthodromically activated fibers in the mammillothalamic and mammillotegmental tracts and antidromically fibers in the fornix for a short distance.

Amygdala↗
PubMed1984

Regeneration of serotonergic fibers in the rat hypothalamus following unilateral 5,7-dihydroxytryptamine injection.

The time course of degeneration and regeneration of serotonin (5-HT) fibers in the rat hypothalamus was studied with 5-HT immunocytochemistry and [3H]5-HT uptake following unilateral injections of 5,7-dihydroxytryptamine (5,7-DHT) into the dorsolateral hypothalamus. Within 3 days of the lesion, 5-HT fibers in the ipsilateral hypothalamus were swollen and darkly stained for 5-HT. In the contralateral hypothalamus few swollen fibers were apparent and these were generally restricted to the area adjacent to the fornix. Swollen 5-HT fibers were evident in the ipsilateral hypothalamus 3-19 days post-lesion in the medial forebrain bundle (MFB) during which time there was a gradual decrease in their density. In the medial and periventricular areas of the ipsilateral hypothalamus there were essentially no 5-HT fibers 7-30 days post-lesion. Sprouting 5-HT fibers were observed 12-19 days post-lesion. Thirty days post-lesion the density of 5-HT fibers in the MFB appeared normal; however, medial and periventricular areas remained denervated. Fifty days post-lesion there was an apparent bilateral hyperinnervation in the lateral and dorsomedial hypothalamic areas of 5,7-DHT-injected animals as compared to sham-injected animals. The morphological data were paralleled by changes in [3H]5-HT uptake. Seven days post-lesion specific high affinity uptake was reduced to 27% of sham in the ipsilateral hypothalamus and to 53% of sham in the contralateral hypothalamus. By 50 days post-lesion, specific high affinity uptake of [3H]5-HT was 141% of sham in the ipsilateral hypothalamus and 96% of sham in the contralateral hypothalamus.

5,7-Dihydroxytryptamine↗
PubMed1986

The choice of a model for studying the hypothalamus-pituitary interactions in vitro.

Comparative studies on the release of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (Prl) by the whole pituitary, pituitary plus hypothalamus and pituitary-hypothalamus complex (PHC) were undertaken to choose an appropriate model for studying the hypothalamus-pituitary interactions in vitro and to relate the importance of the intact neural connections between pituitary and hypothalamus on hypothalamus-pituitary interactions. Also the effect of including dopamine (DA) at 1 X 10(-7) mol/1 in these different in vitro systems on the release of LH, FSH and Prl was investigated. The pituitary released increasing amounts of LH and FSH at 2, 4 and 6 h but the amount of Prl released remained unchanged. The rates of release of LH, FSH and Prl by the pituitary were different and were characteristic of each hormone. Co-incubation of pituitary with hypothalamus stimulated the release of LH and FSH but inhibited the release of Prl. Pituitary-hypothalamus complex behaved almost identical to behaved almost identical to pituitary plus hypothalamus system. Inclusion of 1 X 10(-7) M DA in the incubation medium stimulated the release of LH (80%) but inhibited the release of Prl (71%) by PHC. FSH was unaffected. DA had no significant effect on the release of LH, FSH and Prl by pituitary and pituitary plus hypothalamus systems. It is suggested that PHC is the system of choice for studying hypothalamus-pituitary interactions in vitro.

Animals↗
PubMed1991

Olfactory projections to the hypothalamus.

Electrophysiological recording, together with anterograde and retrograde axonal tracers, was used to provide a comprehensive description of the origin and distribution of the olfactory input to the lateral hypothalamus. This input was much more substantial to the caudal part of the hypothalamus than to the rostral part and originates from several different areas of the olfactory cortex. Positive responses to electrical stimulation of the olfactory bulb were found consistently in the postero-lateral hypothalamus, but only occasionally at more rostral levels. In agreement with this, injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) in the posterior half of the lateral hypothalamus labeled cells in four cortical areas that receive input from the olfactory bulb: the anterior olfactory nucleus, the piriform cortex (in the deepest layer or ventral endopiriform nucleus), the olfactory tubercle (in the deep polymorphic layer), and the anterior cortical nucleus of the amygdala. Injections of WGA-HRP in the anterolateral hypothalamus labeled cells only in the anterior cortical nucleus of the amygdala. Anterograde axonal tracing confirmed these projections. Injections of 3H-leucine in the anterior olfactory nucleus, the piriform cortex, and the olfactory tubercle produced axonal label that was light and confined to the medial forebrain bundle in the rostral hypothalamus but was more substantial and extended throughout the lateral hypothalamic area caudally. Injections in the anterior cortical amygdaloid nucleus labeled axons in the anterior hypothalamus and in the premammillary nuclei as well as in the posterolateral hypothalamic area. In addition, a projection was demonstrated to the nuclei gemini from the polymorphic zone deep to the olfactory tubercle. Injections of two fluorescent retrograde tracers into the mediodorsal nucleus of the thalamus and the posterolateral hypothalamus showed that cells projecting to both diencephalic sites were intermingled in all of the olfactory cortical areas except the anterior olfactory nucleus, where cells were labeled only from the hypothalamus. In the deep layer of the piriform cortex and in the anterior cortical amygdaloid nucleus cells were also double labeled, indicating that they send collateral axons to both parts of the diencephalon.

Amygdala↗
PubMedDate not supplied

5-HT autoreceptors in the regulation of 5-HT release from guinea pig raphe nucleus and hypothalamus.

5-HT autoreceptors involved in the regulation of 5-HT release in the guinea pig dorsal raphe nucleus have been studied in comparison with those in the hypothalamus. In vitro release was measured in slices of raphe and hypothalamus prelabelled with [3H]5-HT, superfused with Krebs solution and depolarized electrically. The non-selective 5-HT receptor agonist, 5-carboxamidotryptamine (5-CT) (0.1-10 nM for raphe: 1-100 nM for hypothalamus) and antagonist, methiothepin (10-1000nM), decreased and increased, respectively, the release of [3H]5-HT evoked by electrical stimulation in either of these regions when given alone. The selective 5-HT1B/D receptor antagonist, GR127935 (100-1000 nM), and the 5-HT1D receptor antagonist, ketanserin (300-1000 nM), had no significant effect on this release in either of these regions. Methiothepin and GR127935 (100-1000 nM) shifted to the right the concentration-effect curve of 5-CT in both the raphe and the hypothalamus. At 300 nM, ketanserin shifted to the right the concentration-effect curve of 5-CT in the raphe but did not modify the 5-CT curve in the hypothalamus. In microdialysis experiments ketanserin, applied locally at 10 microM, increased the extracellular levels of 5-HT in the dorsal raphe nucleus of the freely moving guinea pig, whereas 5-HT levels were unchanged in the hypothalamus. Ketanserin at 1 microM did not affect the decrease in 5-HT output induced by the selective 5-HT1B/D receptor agonist, naratriptan (used at 10 microM in raphe and 0.1 microM in hypothalamus), in the raphe or the hypothalamus. In the raphe, WAY100635, a 5-HT1A receptor antagonist, at 1 microM, did not prevent naratriptan (10 microM) from reducing the extracellular levels of 5-HT. These results suggest that, in the conditions used in this study, the release of 5-HT in the dorsal raphe nucleus is possibly modulated in part by 5-HT1B receptors but essentially the control is through 5-HT receptors whose subtype is still to be determined. In the hypothalamus, however, it is clear that only 5-HT1B receptors are involved in the modulation of 5-HT neurotransmission.

Animals↗
PubMed1997

Neonatal androgen manipulation differentially affects the development of monoamine systems in rat cerebral cortex, amygdala and hypothalamus.

Neural tissue during perinatal life is sufficiently plastic to respond to the presence of testicular androgens. Here we studied the effect of neonatal androgen manipulation (castration of male and androgenization of female rats) on monoamine neurotransmitter systems in the cerebral cortex and sexually dimorphic regions of brain (hypothalamus and amygdala). Norepinephrine (NE) and dopamine (DA) concentrations in cortex, amygdala and hypothalamus of rats were assayed by HPLC at days 25, 60, 120, 180, 240 and 300. Results show that NE levels in all groups of rats at day 25 were higher in the hypothalamus (5-9 ng/mg protein) compared to the amygdala (0.5-3 ng/mg protein) and the cortex (0.5-1 ng/mg protein). Levels of DA at day 25 in the hypothalamus and the amygdala were comparable (up to 3.5 ng/mg) but higher than in the cortex (1.25-1.75 ng/mg protein). NE and DA concentrations in sham-castrated male and androgen-treated females were higher at day 25 compared to castrated male and control females in both amygdala and hypothalamus; however, levels of NE and DA remained unchanged in the cortex. Pattern of NE concentrations started reversing with increase in age, i.e., NE levels in control females and castrated males increased almost 4-fold in amygdala and 2-fold in hypothalamus by day 300, but there was no significant change in the cortex. Compared to that, NE levels decreased in sham-castrated male (2-fold) and androgen-treated females (3-fold) in amygdala as well as in the hypothalamus (2-fold) in both these groups. A similar pattern of reversal of DA levels was found in both amygdala and hypothalamus, however, at day 300 DA levels were comparable in all the four groups. These studies suggest that androgen manipulation (castration or androgen administration) induces age-dependent short- and long-term effects on the development of noradrenergic and dopaminergic systems in the sexually dimorphic regions of brain, amygdala and hypothalamus, without a significant change in the cerebral cortex.

Amygdala↗
PubMed1984

An increase in single unit activity of the medial basal hypothalamus occurs during the progesterone-induced luteinizing hormone surge in the female rhesus monkey.

Accumulated evidence from our laboratory indicates that a positive feedback effect of progesterone (P) occurs at the hypothalamic level. The present study in female rhesus monkeys examined the effects of P on single unit activity of neurons in the hypothalamus and on LH release. Single unit activity was recorded by inserting a flexible stainless steel electrode into the hypothalamus of the monkey, which was restrained in a chair under light ketamine sedation. The firing rate of the single unit activity of the ventral hypothalamus (1.5 +/- 0.2 spikes/sec; n = 57) in ovariectomized estrogen-primed monkeys was slow and was slower in the ventral hypothalamus than in the dorsal hypothalamus (6.2 +/- 0.8 spikes/sec; n = 80). P injection resulted in a dramatic increase in unit activity of the ventral hypothalamus (4.7 +/- 0.6 spikes/sec; n = 111), but not of the dorsal hypothalamus (5.3 +/- 0.7 spikes/sec; n = 72), and induced a concomitant release of LH. Both increases in circulating LH and unit activity of the ventral hypothalamus were significantly correlated over time (P less than 0.02). In contrast, oil injections induced neither change. Therefore, in the rhesus monkey, P seems to activate neural substrates in the ventral hypothalamus to promote the release of LHRH and, subsequently, LH.

Animals↗
PubMed2001

Changes in monoaminergic activity in the anterior, medium and posterior hypothalamus, gonadotropins levels and ovarian hormones during puberty of the female rat.

The aim of present study is the analysis of monoamines concentrations changes in the anterior, medium and posterior hypothalamus, as well as changes in serum gonadotropins levels, ovarian steroids and follicular growth during the prepubertal development of the female rat. Noradrenergic activity in the anterior, medium and posterior hypothalamus reached highest level at day 13 after birth, followed by a subsequent decrease from day 15 to 19 and an increase on days 22 and 27 postnatal. At day 1, neural activity in the medium hypothalamus was higher than the activity in the anterior and posterior hypothalamus. Serotoninergic activity in three portions of the hypothalamus was higher throughout the prepubertal development. Follicle-stimulating hormone and luteinizing hormone serum levels increased between days 11 and 17 and decreased from day 19 to 36. The concentration of 17beta-estradiol was consistently low throughout the prepubertal development and increased at day 39 after birth. These results indicate that during the prepubertal development of the rat, the three regions of the hypothalamus show significant changes in the monoaminergic neural activity. There is an inverse relationship between the noradrenergic activity on the anterior and medium hypothalamus and serotoninergic activity in the posterior hypothalamus with ovarian steroids during sexual maturation. These changes may be linked to the development of the neuroendocrine processes that modulate gonadotropin secretion and ovarian function.

Animals↗
PubMed1997

Increased mitogen-activated protein kinase expression and activity in white adipose tissue of ventromedial hypothalamus-lesioned rats.

Ventromedial hypothalamus lesions in rats induce hyperphagia and hyperinsulinaemia associated with a rapid growth of white adipose tissue resulting in massive obesity. It has been shown previously that at an early stage after the lesion, during the dynamic phase of obesity, the white adipose tissue is hyper-responsive to insulin. In the present work, we show that the effects of insulin on the autophosphorylation of the insulin receptor and on its tyrosine-kinase activity towards endogenous substrates are similar in intact adipocytes of control and ventromedial hypothalamus lesioned rats. One week after the lesion, the expression of phosphatidylinisitol 3-kinase and RAF-1 kinase, evaluated by Western-blotting, was similar in control and ventromedial hypothalamus lesioned rats. In contrast, an important increase in the expression of extracellular signal regulated kinase 1 protein was observed in white adipose tissue of ventromedial hypothalamus lesioned compared to control animals. No difference in the expression of extracellular signal regulated kinase 1 mRNA was observed in adipose tissue of control and ventromedial hypothalamus lesioned rats, suggesting that a posttranscriptional mechanism is involved in the over-expression of extracellular signal regulated kinase 1. The kinase activity of extracellular signal regulated kinase 1 and 2 is also markedly increased in adipocytes of ventromedial hypothalamus lesioned compared to control rats, both in the basal state and after insulin stimulation. Six weeks after the ventromedial hypothalamus lesion, this increase in mitogen-activated protein kinase expression and activity was still observed in adipocytes of ventromedial hypothalamus lesioned rats. These results suggest that an early and sustained increase in the expression and activity of mitogen-activated protein kinase may participate in the development of white adipose tissue in ventromedial hypothalamus lesioned rats.

Adipocytes↗
PubMed1999

Distribution of estrogen receptor-beta messenger ribonucleic acid in the male sheep hypothalamus.

As a first step in determining possible influences of the newly discovered estrogen receptor (ER)-beta on reproduction, we have localized mRNA for ER-beta within the male sheep hypothalamus using in situ hybridization and a rat ER-beta cRNA probe. Highest amounts of hybridization signal were observed in the preoptic area (POA), bed nucleus of the stria terminalis, paraventricular nucleus, and supraoptic nucleus. Relatively moderate amounts of hybridization signal were observed in the retrochiasmatic area (RCH), anterior hypothalamic area, dorsomedial hypothalamus, and lateral hypothalamus. Only a low level of hybridization signal was observed in the ventromedial hypothalamus, suprachiasmatic nucleus, and arcuate nucleus. The presence of ER-beta mRNA in several areas of the male sheep hypothalamus suggests multiple functions for this receptor. The distribution of ER-beta in the ovine hypothalamus was similar to that described for the rat, suggesting a high degree of functional conservation across species. A role for ER-beta in influencing reproduction is suggested by its presence in the POA and RCH, regions of the hypothalamus that control reproduction.

Animals↗
PubMed2006

Aging-related changes of microglia and astrocytes in hypothalamus after intraperitoneal injection of hypertonic saline in rats.

To examine the aging-related changes of microglia and astrocytes in hypothalamus of rats after intraperitoneal injection of hypertonic saline in rats, old- and young-aged rats were injected with hypertonic saline solution into peritoneal cavity. Lectin histochemical techniques using Ricinus communis agglutinin-1 (RCA-1) and immunocytochemical method employing antibody against glial fibrillary acidic protein (GFAP) were used to demonstrate microglia and astrocytes in the hypothalamus of the rats, and the positively-stained cells were analyzed by computer-assisted image analysis system. Our results showed that the numbers of microglia and astrocytes were significantly increased in the hypothalamus of old-aged rats. After intraperitoneal injection of hypertonic saline, the number of microglia was significantly decreased in the hypothalamus of both young- and old-aged groups. After introperitoneal injection of hypertonic saline, the number of GFAP positive cells was significantly increased in the hypothalamus of young rats, but the number of GFAP positive cells did not show significant change in the hypothalamus of old rats. It is concluded that in the hypothalamus of old-aged rats, the increase of microglia may be related with the aging or degeneration of neurons, and the increase of astrocytes may provide more nourishment required by the aged neurons. The microglia and astrocytes in the hypothalamus of the two group rats may be affected by hypertonic saline, and the response of these cells to the stimuli is characterized by some aging-related changes.

Aging↗
PubMed2005

Decreased apoptosis and increased ornithine decarboxylase activity in the intestinal mucosa of rats with bilateral ventromedial hypothalamus lesions.

BACKGROUND: It has not been clearly demonstrated whether the ventromedial hypothalamus regulates intestinal cell growth. Ornithine decarboxylase is a key enzyme in polyamine synthesis, which plays an important role in intestinal mucosal growth. The aim of this study was to investigate whether bilateral ventromedial hypothalamus lesions affect mucosal cell growth. This was done by evaluating ornithine decarboxylase activity and apoptosis in rat small intestines. METHODS: Bilateral ventromedial hypothalamus lesions were produced by thermocoagulation, done with rats under halothane anesthesia 7 days before the experiments. Rats with lesions were pair-fed with sham-operated rats. Total (truncal) vagotomy was performed before the development of ventromedial hypothalamus lesions. Ornithine decarboxylase activity and apoptosis were evaluated in the jejunal mucosa. RESULTS: Ornithine decarboxylase activity in the jejunal mucosa increased significantly 1 week after the development of the bilateral ventromedial lesions, and was attenuated by truncal vagotomy. Apoptosis in the jejunal mucosa was suppressed in rats with ventromedial hypothalamus lesions. In contrast to the effect on ornithine decarboxylase activity, the truncal vagotomies had no effect on apoptosis in rats with lesions. Apoptosis increased in the sham-operated rats after 24-h and 48-h fasting. Apoptosis in the jejunal mucosa of rats with ventromedial hypothalamus lesions did not increase after 24-h fasting. After 48-h fasting, jejunal apoptosis increased in rats with lesions, but not markedly. CONCLUSIONS: The ventromedial hypothalamus may regulate cell growth in the intestinal mucosa partly through the vagal nerve; however, the vagal nerve was not related to intestinal apoptosis controlled by the ventromedial hypothalamus.

Animals↗
PubMed1983

Histamine and the hypothalamus.

The chemical tools that could be used to examine the function of histamine in the brain are considered together with the evidence linking histamine specifically with the hypothalamus. The distribution of histamine and the enzymes responsible for its synthesis and metabolism is consistent with there being both mast cells and histaminergic nerve terminals within the hypothalamus. Iontophoresis, mepyramine binding and histamine-stimulated adenylate cyclase studies suggest that both histamine H1- and H2- receptors are present in the hypothalamus. In addition, intracerebroventricularly injected histamine receptor agonists and antagonists affect many functions associated with the hypothalamus such as cardiovascular control, food intake, body temperature control, and pituitary hormones whose release is mediated via the hypothalamus, such as corticotropin, growth hormone, thyroid stimulating hormone, prolactin, gonadotropins and vasopressin. However, only in the case of thyroliberin release, prolactin release, body fluid control and blood pressure control is there evidence yet that such effects are mediated via histamine receptors actually in the hypothalamus. The effects of enzyme inhibitors suggest endogenous histamine may be involved in the physiological control of thyroid stimulating hormone, growth hormone and blood pressure, and the effects of receptor antagonists support a role for endogenous histamine in prolactin control. Otherwise, there is little evidence for a physiological role for endogenous, as against exogenous, histamine whether it be from histaminergic terminals or mast cells. In addition, few studies have tried to distinguish possible effects on presynaptic receptors, postsynaptic receptors, hypothalamic blood vessels or the hypophyseal portal blood vessels. It is concluded that although there is good evidence now linking histamine and the hypothalamus more specific studies are required, for instance using microinjection or in vitro techniques and the more specific chemical tools now available, to enable a clearer understanding of the physiological role of histamine in the hypothalamus.

Adrenocorticotropic Hormone↗
PubMed2005

Cytokine modulation of defensive rage behavior in the cat: role of GABAA and interleukin-2 receptors in the medial hypothalamus.

Defensive rage behavior is a form of aggressive behavior occurring in nature in response to a threatening stimulus. It is also elicited by stimulation of the medial hypothalamus and midbrain periaqueductal gray (PAG) and mediated through specific neurotransmitter-receptor mechanisms within these regions. Since interleukin (IL)-2 modulates the release of neurotransmitters linked to aggression and rage, we sought to determine whether IL-2 microinjected into the medial hypothalamus would modulate defensive rage. Microinjections of relatively low doses of IL-2 into the medial hypothalamus significantly suppressed defensive rage elicited from the PAG in a dose-dependent manner and in the absence of signs of sickness behavior. Pre-treatment with an antibody directed against IL-2Ralpha or a GABA(A) receptor antagonist blocked IL-2's suppressive effects upon defensive rage. Since the suppression of defensive rage is also mediated by 5-HT(1) receptors in the medial hypothalamus, a 5-HT(1) antagonist was microinjected into this region as a pretreatment for IL-2; however, it did not block IL-2's suppressive effects. Immunocytochemical data provided anatomical support for these findings by revealing extensive labeling of IL-2Ralpha on neurons in the medial hypothalamus. IL-2 microinjected into the medial hypothalamus did not modulate predatory attack elicited from the lateral hypothalamus. In summary, we provide evidence for a novel role for IL-2 in the medial hypothalamus as a potent suppressor of defensive rage behavior. These effects are mediated through an IL-2-GABA(A) receptor mechanism.

Aggression↗
PubMed1998

Distribution and regulation of aromatase activity in the ram hypothalamus and amygdala.

Conversion of androgen to estrogen within the brain by cytochrome P450 aromatase is a component of the system controlling the display of normal male reproductive behavior and negative feedback inhibition of LH secretion in rams. In the present study, we used the highly sensitive 3H2O assay to measure aromatase activity in microdissected regions of the basal diencephalon and amygdala of intact and castrated rams. We found that aromatase activity was heterogeneously distributed. The highest activity was found in the medial amygdala, cortical amygdala, and bed nucleus of the stria terminalis. Intermediate levels of aromatase activity were found within the medial preoptic area/anterior hypothalamus, periventricular preoptic area, lateral preoptic area/anterior hypothalamus, ventromedial hypothalamus, and lateral hypothalamus. The lowest activity was present in the septum, infundibulum/median eminence, and dorsal medial hypothalamus. After castration, aromatase was significantly reduced in the medial preoptic area/anterior hypothalamus, periventricular preoptic area, lateral preoptic area/anterior hypothalamus, and infundibular nucleus/median eminence. In contrast, levels in castrate rams were unchanged in several other regions, most notably the bed nucleus of the stria terminalis and medial and cortical amygdala. These results provide a quantitative profile of aromatase activity in discrete regions of the ram hypothalamus and limbic system. They also demonstrate that aromatase activity is reduced in some, but not all brain regions after castration which suggests that different regulatory mechanisms control aromatase within different neuronal populations of the ram.

Amygdala↗
PubMed2003

Enhanced nitric oxide release/synthesis in the posterior hypothalamus during nitroglycerin tolerance in rats.

We have recently observed that increasing central noradrenergic transmission and sympathomimetic activity is involved with the complex hemodynamic effects during tolerance to nitroglycerin. The present study was to examine the release of nitric oxide (NO) in the posterior hypothalamus during tolerance to depressor responses to nitroglycerin and determine if, during the tolerance, endogenous NO synthesis is induced in the posterior hypothalamus. A microdialysis probe was implanted in the posterior hypothalamus and perfusion fluid was pumped through the probe at 2 microl/min in conscious rats. Tolerance to nitroglycerin was produced by three intravenous (i.v.) injections of 1.3 mg nitroglycerin each within 40 min compared to the same administrations of low dose of the drug, sodium nitroprusside and papaverine. Dialysate samples were collected 1 h before and 1 h each after injections for 8 h. Concentrations of nitrite (NO(2)(-)), nitrate (NO(3)(-)), and total nitrite plus nitrate (NO(x)(-)) were quantified in the samples by using chemiluminescence. The dose-response curve for arterial depressor induced by intravenous injection of the challenge doses of nitroglycerin was markedly shifted to the right at the first hour after nitroglycerin tolerance, lasted 3 to 5 h and reversed at 7 h. The dialysate NO(3)(-) and NO(x)(-) concentrations in the posterior hypothalamus were significantly increased at the first hour following nitroglycerin tolerance but were not altered by low dose of the drug, sodium nitroprusside, and papaverine. Nitroglycerin tolerance predominantly caused an increase in NO(3)(-) release in the posterior hypothalamus with no or small amount of changes in dialysate NO(2)(-) and the response was partially inhibited by pretreatment with N(G)-Propyl-L-arginine (NPLA) (1.0 mg/kg, i.p.), an inhibitor of neuronal NO synthesis. The increase of NO release in the posterior hypothalamus occurred at the first hour, lasted 2 to 3 h and reversed at 5 to 6 h during nitroglycerin tolerance. The results show that systemically administered high dose of nitroglycerin increases NO release in the posterior hypothalamus which matches the time interval of tolerance to arterial depressor response to the drug. Data suggest that there is an enhanced endogenous NO synthesis in the posterior hypothalamus which may affect central sympathetic functions during nitroglycerin tolerance.

Animals↗
PubMed1990

Subicular projections to the hypothalamus and brainstem: some novel aspects revealed in the rat by the anterograde Phaseolus vulgaris leukoagglutinin (PHA-L) tracing method.

The efferent projections from the subiculum to the hypothalamus were examined in the rat by using the anterograde PHA-L tract-tracing method. The density of the subicular projections to the hypothalamus increases at successively more ventral levels of the subiculum. The ventral tip of the region projects to the hypothalamus via 3 different routes: the postcommissural fornix, the medial corticohypothalamic tract (mht) and a ventral pathway running via the amygdala. The fibers in the fornix innervate the median subgroup of the mammillary bodies and, through collaterals, also the lateral hypothalamus. Axons innervating the medial preoptic area, anterior hypothalamus, ventromedial and dorsomedial nuclei as well as the median part of the mammillary nucleus run in the mht. The ventral pathway innervates the supraoptic and medial preoptic nuclei as well as the lateral hypothalamus. Taken together, efferents of the ventral subiculum reach most major areas situated along the longitudinal axis of the hypothalamus. Importantly, however, subicular efferents reach beyond the hypothalamus: PHA-L immunoreactive axons were traced into the mesencephalic central gray and medulla. These anatomical findings show that highly processed cortical information may reach hypothalamic and brainstem areas involved in the integration of endocrine and autonomic functions as well as motivated behaviors.

Animals↗
PubMed1999

Ovarian steroid effects on serotonin 1A, 2A and 2C receptor mRNA in macaque hypothalamus.

This study mapped the location of serotonin (5HT) 1A, 2A and 2C receptor mRNA expression in the female macaque hypothalamus and determined whether the expression was regulated by estrogen plus or minus progesterone treatment using in situ hybridization (ISH) and densitometric analysis of autoradiographic films. The experimental groups of pigtail macaques (Macaca nemestrina) were spayed controls (n=4), estrogen treated (28 days, n=4) and estrogen+progesterone-treated animals (14 days estrogen+14 days estrogen and progesterone, n=4). Monkey specific 5HT1A (432 bp), 2A (411 bp) and 2C (294 bp) receptor probes were generated with PCR. Moderate 5HT1A receptor hybridization signal was detected in the preoptic area and the ventromedial nuclei. Less intense 5HT1A receptor signal was detected in a contiguous area from the dorsomedial nuclei through the posterior hypothalamus and in the supramammillary area. There was no change in 5HT1A receptor hybridization signal in any area with ovarian steroid treatment. Dense 5HT2A receptor hybridization signal was morphologically confined to the paraventricular, supraoptic, and mammillary nuclei and the external capsule of the thalamus. Light 5HT2A mRNA signal was inconsistently observed in the ventromedial nuclei. There was no change in the 5HT2A receptor hybridization signal in any area with ovarian steroid treatment. The 5HT2C receptor mRNA was widely distributed in the macaque hypothalamus. The preoptic area and anterior hypothalamus were largely positive for 5HT2C mRNA with a more concentrated signal in a narrow periventricular area. Dense 5HT2C receptor signal was detected lateral to the ventromedial nuclei (capsule), in the tuberomammillary nuclei, arcuate nucleus, dorsomedial nuclei, infundibular area and choroid plexus. Moderate 5HT2C receptor signal was detected in the ventromedial nuclei, lateral hypothalamus and dorsal to posterior hypothalamus. There was a significant decrease in total 5HT2C mRNA hybridization signal with ovarian steroid treatment in the ventromedial nuclei, dorsal and posterior hypothalamus. In summary, macaque 5HT1A, 2A and 2C receptor mRNAs are located in distinct hypothalamic loci which play a role in a number of autonomic functions and behavior. Ovarian steroids decreased the expression of 5HT2C receptor mRNA in the ventromedial nuclei, dorsal and posterior hypothalamus. The expression of 5HT1A and 5HT2A receptor mRNA was not altered by treatment with ovarian steroids.

Animals↗