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Regional distribution of human growth hormone-releasing hormone in the human hypothalamus by radioimmunoassay.

The regional distribution of human GH-releasing hormone (hGHRH) in the hypothalamus was determined by RIA using a standardized microdissection technique. The antiserum used in the RIA is highly specific for human GHRH-44, and cross-reactivity to hGHRH-40 is minimal (less than 0.06%). The concentration and content of immunoreactive hGHRH-44 (IR-GHRH) were measured in extracts of 12 nuclei and areas microdissected from hypothalami from 5 autopsy subjects. Extracts of proximal and distal pituitary stalk were similarly analyzed for IR-GHRH. The highest concentration of IR-GHRH in the hypothalamus was in the infundibular nucleus, with lesser concentrations in the periventricular area and paraventricular and supraoptic nuclei. All other regions had measurable concentrations, except the mammillary nuclei. There was 56.1 +/- 12.4 (+/- SD) ng (11.1 +/- 1.2 pmol) IR-GHRH in the human hypothalamus and pituitary stalk, with 62% in the pituitary stalk. IR-GHRH in tissue extracts produced the same dose-response curve as did hGHRH in the RIA and coeluted with synthetic hGHRH-44 on gel filtration. Our results indicate the following. 1) The regional distribution of IR-GHRH in the human hypothalamus differs from the regional distributions of other neuropeptides. 2) The infundibular nucleus contains the greatest IR-GHRH regional concentration, in accord with immunohistochemical studies. 3) Appreciable concentrations of IR-GHRH are found in regions not previously identified by immunohistochemical techniques. 4) The IR-GHRH molar content in the hypothalamus-pituitary stalk is lower than that reported for other hypothalamic releasing hormones.

Adult↗

Patterning of the basal telencephalon and hypothalamus is essential for guidance of cortical projections.

We have investigated the mechanisms that control the guidance of corticofugal projections as they extend along different subdivisions of the forebrain. To this aim, we analyzed the development of cortical projections in mice that lack Nkx2-1, a homeobox gene whose expression is restricted to two domains within the forebrain: the basal telencephalon and the hypothalamus. Molecular respecification of the basal telencephalon and hypothalamus in Nkx2-1-deficient mice causes a severe defect in the guidance of layer 5 cortical projections and ascending fibers of the cerebral peduncle. These axon tracts take an abnormal path when coursing through both the basal telencephalon and hypothalamus. By contrast, loss of Nkx2-1 function does not impair guidance of corticothalamic or thalamocortical axons. In vitro experiments demonstrate that the basal telencephalon and the hypothalamus contain an activity that repels the growth of cortical axons, suggesting that loss of this activity is the cause of the defects observed in Nkx2-1 mutants. Furthermore, analysis of the expression of candidate molecules in the basal telencephalon and hypothalamus of Nkx2-1 mutants suggests that Slit2 contributes to this activity.

Animals↗

Aconitine induces bradycardia through a transmission pathway including the anterior hypothalamus in conscious mice.

Aconitine administered intraperitoneally (i.p.) produces bradycardia mainly by a central muscarinic action. The involvement of hypothalamic regions in the occurrence of aconitine-induced bradycardia was investigated in hypothalamus-lesioned mice. The lesions were made by passing a direct current (1.5 mA, 13 s) through a monopolar electrode. The aconitine (30 micrograms/kg, i.p.)-induced bradycardia was prevented by bilateral lesions of either the whole hypothalamus, except for the lateral hypothalamus area, or the anterior hypothalamus (AH). The bradycardia was not prevented by bilateral lesions of the ventromedial, the paraventricular, the posterior or the lateral hypothalamus regions. Bupivacaine, but not atropine (1 microgram, administered into the intact AH) prevented aconitine-induced bradycardia in mice with a contralaterally lesioned AH. Aconitine (0.8 microgram) directly administered into the unilateral AH in intact mice caused a late phase and lesser extent of bradycardia. These results suggest that a transmission pathway including the AH contributes to the aconitine-induced bradycardia but does not involve the activation of muscarinic receptors in the AH.

Aconitine↗

Effects of acute and chronic administration of MCI-225, a new selective noradrenaline reuptake inhibitor with 5-HT3 receptor blocking action, on extracellular noradrenaline levels in the hypothalamus of stressed rats.

In the present study, we investigated the effects of acute and chronic systemic administration of MCI-225 (4-(2-fluorophenyl)-6-methyl-2-(1-piperazinyl)thieno[2,3-d]pyrimidine monohydrate hydrochloride), a newly-developed selective noradrenaline (NA) reuptake inhibitor with 5-HT3-receptor-blocking action, on extracellular NA levels in the hypothalamus of stressed and non-stressed rats by utilizing intracerebral microdialysis. Acute administration of MCI-225 (3 and 10 mg/kg, p.o.) significantly and dose-dependently increased extracellular NA levels in the hypothalamus in non-stressed rats. Footshock for 20 min also significantly increased NA levels in the hypothalamus of both groups of rats pretreated with vehicle and MCI-225. Although chronic administration of MCI-225 (3 or 10 mg/kg, p.o. for 14 days) did not alter the basal extracellular NA levels in the hypothalamus, the stress-induced increases in extracellular NA levels were significantly lower in rats chronically treated with MCI-225 (10 mg/kg) than those of rats pretreated with vehicle for the same period. The increase in extracellular NA levels induced by MCI-225 challenge (3 or 10 mg/kg, p.o.) were not different between rats chronically treated with MCI-225 or vehicle. These results suggest that MCI-225 enhances extracellular NA levels in the hypothalamus in both non-stressed and stressed rats by inhibiting NA uptake and that chronic systemic administration of MCI-225 did not alter basal extracellular NA levels, but reduced the increase in NA release caused by footshock stress. These data suggest the possibility that MCI-225 might possess anxiolytic and/or antidepressant properties.

Adrenergic Uptake Inhibitors↗

Regulation of CRF, POMC and MC4R gene expression after electrical foot shock stress in the rat amygdala and hypothalamus.

We investigated the effects of electrical foot shock stress on the melanocortin signaling cascade and the hypothalamus-pituitary-adrenal (HPA) system by observing levels of mRNA expression of corticotropin releasing factor (CRF), pro-opiomelanocortin (POMC), and melanocortin receptor subtype 4 (MC4R) in the rat amygdala and hypothalamus. When rats were exposed to electrical shock for 0.5 hr or 1 hr, plasma ACTH and corticosterone concentrations increased, indicating stress. The rats were then sacrificed to obtain RNA preparations from the brain tissue. In the amygdala, the expression of MC4R and POMC mRNA as well as CRF mRNA was significantly increased by electrical foot shock stress. In the hypothalamus, MC4R and POMC mRNA increased, but CRF mRNA remained unchanged. The duration of increased gene expression of MC4R and POMC in the amygdala was more sustained than in the hypothalamus. These results have provided the first evidence that exposure to stress increases expression of the MC4R system in the amygdala and hypothalamus.

Amygdala↗

Receptor phosphorylation mediates estradiol reduction of alpha2-adrenoceptor coupling to G protein in the hypothalamus of female rats.

Estrogen increases evoked norepinephrine release in the hypothalamus of female rodents, in part by reducing the ability of alpha2-adrenoceptors to act as negative feed-back inhibitors of norepinephrine release. Estrogen enhancement of norepinephrine release in the hypothalamus correlates with decreased coupling of the alpha2-adrenoceptor to G protein. To determine the mechanism by which estrogen uncouples alpha2-adrenoceptors from G protein, we tested the hypothesis that estrogen increases alpha2-adrenoceptor phosphorylation. Short-term activation of endogenous serine/threonine phosphatases with protamine or treatment with exogenous phosphatase restored alpha2-adrenoceptor coupling to G protein to control levels in hypothalami from estrogen-exposed female rats. Additional experiments examined whether estrogen alters G protein-coupled receptor kinase expression or activity or serine/threonine phosphatase activity. These proteins are involved in G protein-coupled receptor phosphorylation, internalization, and recycling. Estrogen exposure reduced G protein-coupled receptor kinase mRNA, protein, and activity in the hypothalamus. Furthermore, estrogen treatment reduced serine/threonine phosphatase activity in the hypothalamus. Analysis of ligand binding in subcellular fractions demonstrated that estrogen decreases the fraction of internalized alpha2-adrenoceptors in the hypothalamus.Therefore, estrogen promotes norepinephrine release in the hypothalamus by stabilizing alpha2-adrenoceptor phosphorylation, uncoupling the receptor from G protein. Estrogen may stabilize alpha2-adrenoceptor phosphorylation by inhibiting receptor internalization and dephosphorylation.

Adrenergic alpha-Antagonists↗

[Estrogen formation in the central nervous system and characteristics of aromatase of rat hypothalamus].

Estrogen formation from androst-4-ene-3,17-dione and its kinetics were studied using microsomes from rat hypothalamus. [4-14C] androst-4-ene-3,17-dione and a homogenate of rat hypothalamus were incubated in the presence of NADPH at 37 degrees C for 3 hrs. The estrogen fraction was extracted from the incubation mixture with ethyl acetate, purified by column chromatography on Sephadex LH-20 and Bond Elut C18, and separated into estrone and estradiol fractions by HPLC. In analysis of the trimethylsilyl (TMS) derivatives of each fraction by gas chromatography-mass spectrometry (GC-MS), the molecular ion peak of the estrone fraction appeared at m/z 344, within 2 amu of that for the TMS derivative of natural estrone. The retention time of the estrone fraction derivative was 11.6 min, the same as that of natural estrone. 14C-estrone was thus concluded to be biosynthesized from [4-14C]-androst-4-ene-3,17-dione in rat hypothalamus. The kinetics of the aromatase of rat hypothalamic tissue was studied by measuring 3H2O released from [1 beta-3H]-androst-4-ene-3,17-dione and estrone as the estrogen product by measured gas chromatography selected ion monitoring (GC-SIM). High correlation was found between 3H2O release and estrone measured by GC-SIM (r = 0.97). Aromatase activity was linear with respect to incubation time and quantity of tissue. Km and Vmax were 30.3 nM and 7.98 fmol estrogen/h/mg of wet tissue, respectively. 4-hydroxyandrostenedione (4-OH-A) suppressed the activity of aromatase in both rat hypothalamic and human placental tissue in a concentration-dependent manner. Polyclonal IgG to human placental aromatase also suppressed aromatase activity of human placental tissue, but only slightly suppressed that of rat hypothalamus. The molecular structure of aromatase in rat hypothalamus was thus concluded to differ from that in human placenta.

Androstenedione↗

Effect of aging on the activities of acetylcholinesterase, Na+,K(+)-ATPase and Mg(2+)-ATPase in rat pituitary and hypothalamus.

Acetylcholinesterase (AChE), Na+,K(+)-ATPase and Mg(2+)-ATPase activities were estimated in homogenised rat pituitary and hypothalamus of 4- and 22-month-old rats. AChE activity was not altered in the pituitary of aged compared to adult rats, while it was found decreased by about 40% in the hypothalamus. Na+,K(+)-ATPase activity remained stable in the hypothalamus, while it was decreased by about 38% in the pituitary. Mg(2+)-ATPase activity remained unchanged in the hypothalamus, but was increased by about 83% in the pituitary. This pituitary Na+,K(+)-ATPase inactivation may result in pathological mood and decreased neural excitability and metabolic energy production in aged animals. The age-related alterations of AChE, Na+,K(+)-ATPase and Mg(2+)-ATPase activities may reflect changes in secretion and responses of some hormones of pituitary and hypothalamus.

Acetylcholinesterase↗

Enhanced norepinephrine release in hypothalamus from locus coeruleus in SHR.

The hypothesis that a functional projection from the locus coeruleus (LC) to the posterior hypothalamus contributes to the development of hypertension in SHR, was tested by measuring norepinephrine (NE) in the posterior hypothalamus by brain dialysis after injections of L-glutamate (L-glu) into LC. L-glu elicited a prolonged elevation of blood pressure in both SHR and WKY. Pressor effects were significantly larger in SHR than in WKY. Extracellular NE in the posterior hypothalamus increased after LC stimulation; NE release was significantly higher in SHR than in WKY. Injections of 6-hydroxydopamine (6-OHDA) into posterior hypothalamus lowered the resting blood pressure and attenuated the pressor responses to L-glu injections into the LC in SHR. These findings suggest that the LC projects functionally to the posterior hypothalamus and that the projection can contribute to the development of hypertension in SHR.

Animals↗

Differential qualitative and temporal changes in the response of the hypothalamus-pituitary-adrenal axis in rats after localized or total-body irradiation.

Stress such as exposure to ionizing radiation is able to activate the hypothalamus-pituitary-adrenal axis. The present study sought to examine the effects of different configurations of a 10-Gy gamma irradiation in rats on the hypothalamus-pituitary-adrenal axis to understand the mechanism of negative feedback by glucocorticoids induced by ionizing radiation. Specifically, we determined adrenocorticotropin and corticosterone levels in plasma as well as corticotrophin-releasing factor expression in the paraventricular nucleus of the hypothalamus by in situ hybridization from 6 h to 4 days after total-body, abdominal or head irradiation. In this study, we found an activation of the hypothalamus-pituitary-adrenal axis after radiation exposure. Plasma adrenocorticotropin and corticosterone levels were significantly increased after total-body and abdominal irradiation 3 days after exposure, in parallel with decreased labeling of corticotrophin-releasing factor mRNA in the parvocellular region of the paraventricular nucleus of the hypothalamus. Our results suggest that ionizing radiation activates the neuroendocrine system to protect the organism from the occurrence of radiation-induced inflammation.

Adaptation, Physiological↗

Pro-opiomelanocortin processing in the hypothalamus: impact on melanocortin signalling and obesity.

Bioactive peptides derived from the prohormone, pro-opiomelanocortin (POMC), are generated in neurons of the hypothalamus and act as endogenous ligands for the melanocortin-4 receptor (MC4R), a key molecule underlying appetite control and energy homeostasis. It is therefore important to understand many aspects of POMC gene regulation in the brain, as pharmacological manipulation of POMC expression/processing could be a potential strategy to combat obesity. Most studies that have analysed POMC gene expression in the hypothalamus have focused on gene transcription experiments. Ultimately, however, factors that regulate post-translational processing and secretion of peptides will have most bearing on melanocortin signalling. This article focuses on (a) current evidence that POMC is involved in obesity, (b) how POMC transcription is regulated in the hypothalamus, (c) the mechanism by which proteolytic processing of POMC is controlled in the hypothalamus and what peptides are produced and (d) which POMC-derived peptides are the most potent ligands at the melanocortin receptor in vitro and in vivo. It seems that post-translational cleavage of POMC in the hypothalamus may be regulated with respect to energy requirement. We predict that further research into hypothalamic POMC processing, and the proteolytic enzymes involved, may yield important new clues on how flux through the MC4R pathway is regulated.

Animals↗

Distribution of amylin-immunoreactive neurons in the monkey hypothalamus and their relationships with the histaminergic system.

Amylin (AMY) is a 37 amino acid peptide of pancreatic origin that has been localized in peripheral and central nervous structures. Both peripheral and central injection of the peptide causes various effects, including anorectic behavior in rats. Prompted by previous reports showing that the anorectic effect of AMY is mediated by histamine release, we immunohistochemically investigated possible relationships between these two systems at the light microscopical level. Monkey (Macaca fuscata japonica) hypothalamus specimens were submitted to immunohistochemical double staining procedures using AMY and histidine decarboxylase (HDC) antisera. AMY-immunoreactive neurons were found widely distributed in several nuclei of the monkey hypothalamus including the supraoptic, paraventricular, perifornical, periventricular, ventromedial, arcuate, and tuberomammillary nuclei. We detected AMY-immunoreactive nerve fibers throughout the hypothalamus, the median eminence and hypothalamus-neurohypophysial tract. Although AMY- and HDC-immunoreactive neuronal cell bodies occupied distinct hypothalamic zones, many HDC-immunoreactive cell bodies and dendrites, particularly those in the periventricular, arcuate, and rostral tuberomammillary regions, were surrounded by numerous AMY-immunoreactive nerve fiber varicosities. These findings demonstrate for the first time the presence of a discrete number of AMY-immunoreactive neurons in the monkey hypothalamus and add morphological support to the experimental data demonstrating that AMY probably exerts its influence on food intake via the histaminergic system.

Amyloid↗

Exercise improves insulin and leptin sensitivity in hypothalamus of Wistar rats.

Prolonged exercise of medium to high intensity is known to promote a substantial effect on the energy balance of rats. In male rats, moderately to severely intense programs lead to a reduction in food intake. However, the exact causes for the appetite-suppressive effects of exercise are not known. Here, we show that intracerebroventricular insulin or leptin infusion reduced food intake in exercised rats to a greater extent than that observed in control animals. Exercise was associated with a markedly increased phosphorylation/activity of several proteins involved in leptin and insulin signal transduction in the hypothalamus. The regulatory role of interleukin (IL)-6 in mediating the increase in leptin and insulin sensitivity in hypothalamus was also investigated. Treatment with insulin or leptin markedly reduced food intake in exercised rats that were pretreated with vehicle, although no increase in sensitivity to leptin- and insulin-induced anorexia after pretreatment with anti-IL-6 antibody was detected. The current study provides direct measurements of leptin and insulin signaling in the hypothalamus and documents increased sensitivity to these hormones in the hypothalamus of exercised rats in an IL-6-dependent manner. These findings provide support for the hypothesis that the appetite-suppressive actions of exercise may be mediated by the hypothalamus.

Animals↗

Reduced expression of the cystic fibrosis transmembrane conductance regulator gene in the hypothalamus of patients with Alzheimer's disease.

BACKGROUND: The cystic fibrosis transmembrane conductance regulator (CFTR) gene encodes an approximately 150-165 kD glycoprotein that is mutated in individuals with cystic fibrosis. Previous studies demonstrated expression of the CFTR gene in the hypothalamus, suggesting a potential role for this molecule in the regulation of systemic metabolic functions. Individuals with cystic fibrosis often exhibit wasting and marked reductions in body fat content. Since the hypothalamus is a late target of neurodegeneration in Alzheimer's disease (AD), we postulated that patients with end-stage AD and bodily wasting would have reduced levels of CFTR expression in the hypothalamus. METHODS: CFTR mRNA and protein were examined in postmortem hypothalamic tissue from 11 AD and 7 aged controls using in situ hybridization and immunohistochemical staining. Standardized sections that included the supra-optic, paraventricular, anterior, and ventromedial nuclei, and the lateral hypothalamus were studied. RESULTS: The density of CFTR+ neurons and the intensity of the CFTR hybridization signals were strikingly reduced in AD. Immunohistochemical staining studies demonstrated CFTR immunoreactivity most prominently distributed in small clusters of neurites (5 to 20 in number). Digital image quantification showed that the density of CFTR+ neurites was significantly reduced in AD relative to aged control samples (P=0.001). However, there was no evidence for selective involvement of particular hypothalamic nuclei. CONCLUSIONS: CFTR gene expression is down-regulated and its corresponding immunoreactivity reduced in AD relative to control hypothalamic tissue. Reduced CFTR expression in the hypothalamus may represent an important mechanism by which AD neurodegeneration contributes to body wasting in the late stages of disease.

Aged↗

Effects of acupuncturing Tsusanli (ST36) on expression of nitric oxide synthase in hypothalamus and adrenal gland in rats with cold stress ulcer.

AIM: To study the protective effect of acupuncturing Tsusanli (S(T)36) on cold stress ulcer, and the expression of nitric oxide synthase (NOS) in hypothalamus and adrenal gland. METHODS: Ulcer index in rats and RT-PCR were used to study the protective effect of acupuncture on cold stress ulcer, and the expression of NOS in hypothalamus and adrenal gland. Images were analyzed with semi-quantitative method. RESULTS: The ulcer index significantly decreased in rats with stress ulcer. Plasma cortisol concentration was up regulated during cold stress, which could be depressed by pre-acupuncture. The expression of NOS1 in hypothalamus increased after acupuncture. The increased expression of NOS2 was related with stress ulcer, which could be decreased by acupuncture. The expression of NOS3 in hypothalamus was similar to NOS2, but the effect of acupuncture was limited. The expression of NOS2 and NOS3 in adrenal gland increased after cold stress, only the expression of NOS1 could be repressed with acupuncture. There was no NOS2 expression in adrenal gland in rats with stress ulcer. CONCLUSION: The protective effect of acupuncturing Tsusanli (S(T)36) on the expression of NOS in hypothalamus and adrenal gland can be achieved.

Acupuncture↗

Distribution of delta sleep-inducing peptide in the newborn and infant human hypothalamus: an immunohistochemical study.

The distribution of delta sleep-inducing peptide immunoreactive cell bodies, fibers, and terminal-like structures was investigated in the normal human hypothalamus during the first postnatal year, using immunohistofluorescence and peroxidase anti-peroxidase techniques. Immunolabeled perikarya were relatively few and were mostly scattered through the anterior (preoptic) and mediobasal regions (infundibular nucleus) of the hypothalamus. DSIP-immunoreactive fibers and terminal-like fibers were observed throughout the entire rostrocaudal extent of the hypothalamus. They exhibit high densities in the preoptic region, the organum vasculosum of lamina terminalis, infundibular nucleus and median eminence. Moderate to low densities of DSIP-immunoreactive fibers were observed in the other hypothalamic structures, located in the anterior and mediobasal regions of hypothalamus, such as periventricular, paraventricular, suprachiasmatic, ventromedial, dorsomedial and parafornical nuclei. In the present study, the analysis of the immunohistochemical pattern of DSIP-immunoreactive neuronal elements in the human infant hypothalamus during the first postnatal year provided evidence of the presence of several differences. We have found qualitative age-related changes in the density of DSIP immunoreactivity in several hypothalamic structures such as the anterior region and the median eminence.

Delta Sleep-Inducing Peptide↗

[The interrelations between neurons of the amygdala and hypothalamus during conditioning with selection of food reinforcement quality in cats].

Three cats were subjected to appetitive instrumental conditioning to light by the method of the "active choice" of the reinforcement quality. The short-delayed conditioned bar-pressings were reinforced by bread-meat mixture and the delayed response by meat. The animals differed in behavior strategy: two animals preferred bar-pressing with long delay (the so-called "self-control" group) and one animal preferred bar-pressing with short delay (the so-called "impulsive" group). The multiunit activity of the basolateral amygdala and nucleus lateralis of the hypothalamus was recorded through chronically implanted nichrome wire semimicroelecrodes. The interactions between the neighboring neurons in the lateral hypothalamus and basolateral amygdala (within the local neuronal network) and between the neurons of the basolateral amygdala and lateral hypothalamus (distributed neuronal networks in the direction amygdala--hypothalamus and vice versa) were evaluated by means of statistical crosscorrelation analysis of spike trains. The crosscorrelational interneuronal connections in the delay range of 0-100 ms were examined. It was shown that the number of crosscorrelations between the discharges on neurons both in the local networks of basolateral amygdala and distributed networks was significantly higher in "impulsive" cats. In both groups of animals, the percentage of crosscorrelations between neighbouring neurons in the local networks of the lateral hypothalamus was similar. We suggest that the local networks of the basolateral amygdala and amygdalar-hypothalamic distributed neuronal networks are involved in the system of brain structures which determine the individual features of animal behavior.

Amygdala↗

[Effect of Gengnianjian on up regulated estrogen receptor mRNA to substance P and beta-endorphin in hypothalamus of aging female rats].

OBJECTIVE: To investigate the effect of Chinese herbal formula Gengnianjian on estrogen receptor (ER), ERmRNA substance P (SP) and beta-endorphin (beta-EP) in the hypothalamus of aging female rats. METHODS: ER proteins were determined by radioligand binding assay, ER mRNA was analyzed by Northern blot analysis and the levels of beta-EP and SP were detected by immunohistochemistry. RESULTS: In aging rats, lowered ER and ER mRNA in the hypothalamus were still up-regulated by low serum E2 level, but not in rats of after the age of 21 months; Gengnianjian significantly increased ER protein level and ER mRNA expression, decreased SP and increased the level of beta-EP in the hypothalamus in aging female rats before 21 months of age, without changing of serum E2 level. In EB group, serum E2 and beta-EP levels increased and SP level decreased but ER expression suppressed in the hypothalamus except after 21 months. CONCLUSION: Enhance estrogen bioactivity can decrease the level of SP and increase the level of beta-EP in hypothalamus of aging female rats. Herbal formula Gengnianjian increase-EP level and decrease SP level by raising the level of ER and ER mRNA.

Aging↗