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PubMed1979

Sex-related and cyclic variation of trace elements in rat hypothalamus and pituitary.

The concentrations of 7 trace elements--iron, copper, zinc, arsenic, selenium, bromine, and rubidium--in rat hypothalami and anterior pituitaries were measured by X-ray fluorescence spectrometry. Male, cycling female, and oophorectomized animals were studied under different conditions of reproductive function. Hypothalamic zinc and copper concentrations both rose between proestrus and estrus days and fell again at diestrus. After castration, concentrations of iron, copper, and arsenic were decreased in both pituitary and hypothalamus, while zinc concentrations rose. Male rats had lower pituitary concentrations of iron, copper, zinc, arsenic, and rubidium than cycling females. Under these hormonal manipulations, hypothalamus zinc concentration and gonadotropin secretion appear to be correlated. While injections of copper salts into the hypothalamus can also stimulate gonadotropin release, we did not observe any consistent relation between endogenous hypothalamic copper concentrations and gonadotropins.

Animals↗
PubMed1980

Septal and amygdalar efferents to the hypothalamus which facilitate hypothalamically elicited intraspecific aggression and associated hissing in the cat. An autoradiographic study.

Septal and amygdalar sites were identified which facilitated hypothalamically elicited intraspecific agression and associated hissing in cats. Tritiated proline was injected into facilitatory sites through a Hamilton syringe modified to serve as an electrode. Efferents from septal or amygdalar facilitatory sites were traced to the hypothalamus by means of autoradiography. Amygdalar facilitatory sites projected primarily to the core and capsule of the ventromedial nucleus of the hypothalamus (VMH), while septal facilitatory sites projected only lightly to the VMH. Common to all septal facilitatory sites, and not previously reported, was a distinct and considerable projection to the medial hypothalamus, in association with the paraventricular and dorsomedial nuclei. The means by which septal and amygdalar sites may act to facilitate hypothalamically elicited intraspecific aggression are discussed.

Aggression↗
PubMed1980

Afferent projections to quiet attack sites in cat hypothalamus.

Quiet biting attack by a cat on a rat was elicited by electrical stimulation of sites in the cat's lateral hypothalamus. Horseradish peroxidase was deposited at the attack sites. Cells containing reaction products were found in gyrus proreus, anterior and central medial amygdaloid nuclei, lateral and medial preoptic areas, substantia innominata, the bed nuclei of stria terminalis, and anterior commissure. The dorsomedial area of the hypothalamus, paraventricular nucleus, supramammillary region, and posterior hypothalamic area also contained reactive cells. In the midbrain the ventral tegmental area of Tsai, the dorsal and superior central nuclei of the raphe, central gray matter and interpeduncular nucleus were regions with reactive cells. In the pontine region, the locus coeruleus, parabrachial nuclei, nucleus of the lateral lemniscus, and the dorsal tegmental nucleus of Gudden all had reactive cells. There are many structures which send afferent projections to quiet attack sites located in the hypothalamus and the pontine tegmentum. The commonality of afferents to attack sites lends credence to the notion that a complex, distributed, interactive network underlies the neural basis of attack behavior.

Afferent Pathways↗
PubMed1981

Release of endogenous catecholamines from slices of hypothalamus of rats.

The release of endogenous catecholamines from superfused slices of rat hypothalamus was studied under basal conditions and during release evoked by 40 mM K+. Catecholamines in superfusates, and in extracts of the tissue after stimulation, were isolated by column chromatography and quantitated by liquid chromatography with electrochemical detection. Norepinephrine (NE) was not consistently demonstrable in superfusate collected under basal conditions, but 40 mM K+ caused the release of from 2 to 4 ng/g of tissue per min. The addition of cocaine to the superfusate caused increases in basal and evoked release of NE. Epinephrine (E) could be measured in superfusates of slices from male but not female rats and then only when cocaine was added to the superfusate. Accordingly, the concentration of E in hypothalamus was greater in male rats than in female rats. Dopamine (DA) was not consistently measurable in the spontaneous overflow from slices either in the presence or absence of cocaine. K+-evoked release of DA could be demonstrated in slices from female rats. The addition of cocaine increased the evoked release of DA from slices from both sexes. Corticosterone, added to cocaine, had no effects on the efflux of any of the catecholamines. The experiments suggest that neuronal reuptake of all catecholamines is very efficient in the hypothalamus both under basal conditions and during evoked release.

Animals↗
PubMed1981

Presynaptic regulation of the release of catecholamines in the cat hypothalamus.

The posterior hypothalamus of cats was superfused through a push-pull cannula and the release of endogenous catecholamines was determined in the superfusate. Superfusion with yohimbine, isoprenaline, salbutamol or tazolol increased, while superfusion with propranolol decreased, the release of all three catecholamines. Transection of the brain caudal to the hypothalamus inhibited 'resting' and drug-induced release. It is concluded that alpha- and beta-adrenoceptors of the hypothalamus are involved in the regulation of the release of catecholamines.

Albuterol↗
PubMed1982

Distribution of substance P, somatostatin and neurotensin in the human hypothalamus.

The distribution of substance P, somatostatin and neurotensin in the human hypothalamus was studied by radioimmunoassay analysis of 11 nuclei and areas within the hypothalamus, in 10 human post-mortem cases. The samples were microdissected according to a recently developed standardized method. Substance P was present in higher concentrations both rostrally in the hypothalamus, and ventrally. Somatostatin was found predominantly in the basal tuberal region, and neurotensin in the anterior hypothalamic area. The chromatographic behaviour of human hypothalamic neurotensin is also presented.

Adult↗
PubMed1983

Is the knife-cut in the hypothalamus a permanent barrier to regrowth of nerve fibers? -an affirmative answer.

The regenerative capacity of nerve fibers was studied in adult female rats. Horseradish peroxidase was injected into the anterior hypothalamus lateral to the suprachiasmatic nucleus 4 days, 6 weeks and 4 months, respectively, following an archiform retrochiasmatic knife-cut. The trajectory of the stained fibers was examined on horizontal sections of the hypothalamus. No nerve fibers could be seen sprouting across the scar-tissue of the knife-cut regardless of the survival time. In one rat (6-week survival time) a bundle of fine nerve fibers turned in a medial direction at the caudal end of the knife-cut, suggesting that sprouting fibers were destined to reinnervate parts of the deafferented medial-basal hypothalamus.

Animals↗
PubMed1984

Monosodium glutamate lesions in rat hypothalamus studied by immunohistochemistry for gonadotropin releasing hormone, neurotensin, tyrosine hydroxylase, and glutamic acid decarboxylase and by autoradiography for [3H] estradiol.

Adult male and female rats treated neonatally with monosodium glutamate (MSG) exhibit lesions in the arcuate nucleus of the hypothalamus. Immunohistochemical analysis of the distribution of tyrosine hydroxylase (TH), glutamic acid decarboxylase (GAD), neurotensin (NT) and gonadotropin-releasing hormone (GnRH) reveals substantial destructions of tuberoinfundibular dopamine and NT systems accompanied by a marked reduction of immunoreactivity in the median eminence. GAD immunoreactivity in the arcuate nucleus and median eminence is greatly reduced, while GnRH containing structures in the mediobasal hypothalamus are not noticeably affected. Evaluation of autoradiograms after intravenously administered [3H] estradiol in the ventral hypothalamus indicate an almost complete loss of target neurons in the arcuate nucleus but not in the nearby ventromedial nucleus. The results suggest that: (a) NT- and dopamine-containing neurons of the arcuate nucleus project to the median eminence via tuberoinfundibular NT and dopaminergic pathways; (b) GABA in the median eminence originates to a major extent from neurons of the arcuate nucleus through a tuberoinfundibular GABAergic system; (c) GnRH is produced in the rat outside the arcuate nucleus; (d) the MSG-induced lesion in the basal tuberal region abolishes or strongly diminishes estradiol target neurons in the arcuate nucleus.

Animals↗
PubMed1986

GABAergic and catecholaminergic synaptic interactions in the macaque hypothalamus: double label immunostaining with peroxidase-antiperoxidase and colloidal gold.

Immunogold staining (IGS) for glutamic acid decarboxylase (GAD) was combined with the peroxidase-antiperoxidase (PAP) technique for tyrosine hydroxylase (TH) to analyze gamma-aminobutyric acid-catecholaminergic neuronal interactions in the rhesus hypothalamus. At the light-microscopic level, TH-immunoreactive (-IR) perikarya and their fibers (brown) were observed in the anterior ventral periventricular area (AVPV), the arcuate nucleus (ARC) and the adjacent periventricular zone (ARC-PVZ). GAD-IR processes (light red) were also present throughout the hypothalamus and appeared to contact some TH-IR neurons. At the electron-microscopic level, PAP was present in perikarya, dendrites, axons and axon terminals of TH-IR neurons. Colloidal gold particles (15 nm) were found only in dendrites and axon terminals of GAD-IR neurons. Labeled GAD terminals typically contained small, clear synaptic vesicles, while TH terminals contained these and sometimes one or two dense-core vesicles. In the ARC and ARC-PVZ, asymmetrical (Gray I) axodendritic synapses occurred between GAD and TH-IR profiles, with TH/GAD directionality more prevalent. Symmetrical (Gray II) synapses were less common, with either TH or GAD presynaptic in axodendritic and dendrodendritic contacts. GAD/GAD interactions were not observed, but TH/TH contacts appeared to be mostly dendrodendritic. In the AVPV, only symmetrical synapses were encountered, and their directionality was difficult to determine. GAD- and TH-IR dendrites frequently established dendrodendritic synapses, but GAD/TH dendrosomatic synapses were seldom seen. These results illustrate the complex interactions of GAD- and TH-containing elements in the neuroendocrine hypothalamus.

Animals↗
PubMed1986

Changes in the immunoreactivities of an opioid peptide leumorphin in the hypothalamus and anterior pituitary during the estrous cycle of the rat and their relation to sexual behavior.

Leumorphin, an opioid peptide whose functions are unknown, is found in mammalian brain and pituitary and stimulates lordosis behavior in estrogen-treated female rats. To elucidate the role of leumorphin in the physiological control of female sexual behavior, the levels of immunoreactive (ir) leumorphin as well as ir dynorphin (dynorphin A) were measured in the rat brain and pituitary during the estrous cycle. There was a clear variation of ir leumorphin in the hypothalamus and anterior pituitary during the estrous cycle. The levels of ir leumorphin in the hypothalamus and anterior pituitary on the afternoon of proestrus were significantly higher (P less than 0.01) than those on the afternoons of estrus and metestrus. The rise in the hypothalamic levels of ir leumorphin on the afternoon of proestrus was correlated with the receptivity of lordosis during the estrous cycle. Furthermore, there was a close correlation with ir dynorphin levels. These findings are in agreement with studies demonstrating a common precursor for leumorphin and dynorphin. Ir leumorphin in the hippocampus and neurointermediate pituitary did not change significantly during the estrous cycle. Because the leumorphin antiserum used recognizes rimorphin (dynorphin B) 1.78 times more than porcine leumorphin on a molar basis, high performance-gel permeation chromatography was done on pooled extracts of hypothalamus taken at proestrus and estrus. The peak in the leumorphin-like substance in the activation of sexual behavior is discussed.

Animals↗
PubMed1986

The role of the mediobasal arcuate hypothalamus in relation to opioid systems in the control of ingestive behaviour in the rat.

Bilateral, radiofrequency lesions of the mediobasal arcuate hypothalamus (MBH) strongly depleted levels of immunoreactive (ir)-beta-endorphin (beta-EP) in the hypothalamus and other brain tissues: these changes reflect destruction of those beta-EP-containing perikarya which are located in the MBH. No change in plasma ir-beta-EP was seen. The ir-dynorphin (DYN) content of the hypothalamus was also depressed while that of ir-Met-enkephalin was unaffected. The fall in hypothalamic ir-beta-EP was correlated with the fall in that of ir-DYN. Lesioned rats displayed only a minor, transient reduction in rate of weight gain between days 3 and 9 postsurgery: this disappeared thereafter. Further, the lesion did not affect the pattern of weight loss and regain associated with 24 h food and water deprivation. Indeed, the total 24 h (daily) food intake (FI) and water intake (WI) of lesioned rats did not differ from that of sham animals while deprivation-induced hyperphagia and hyperdipsia was not attenuated by the lesions. Moreover, the ability of naltrexone to decrease FI and WI (during both dark and light phases of the daily cycle) was not altered by the lesions. These observations indicate that central beta-EP may not be essential for the maintenance of a normal 24 h FI and WI and that opioid antagonists do not act upon the MBH or upon central beta-EP neurones in their suppression of FI and WI. Further, they suggest that central beta-EP may not fulfil an essential role in the control of body weight in the rat. Lesioned rats did, however, reveal a shift in the diurnal rhythmicity of FI and WI reflected in a reduction in the dark:light ratios of these. An alteration in the diurnal rhythmicity of sleeping and core temperature, but not locomotor activity, was also seen. The shifts in hypothalamic ir-beta-EP and ir-DYN (but no other tissue levels of any peptide) were correlated with the magnitude of the shifts in diurnal rhythmicity of ingestive behaviour. Moreover, lesions caudal to the MBH (not affecting hypothalamic ir-beta-EP or ir-DYN) or dexamethasone treatment (which affects pituitary pools of ir-beta-EP and ir-DYN) did not modify these rhythms. Thus, in these respects, the effects are 'particular' to MBH lesions modifying hypothalamic ir-beta-EP and ir-DYN. The data suggest that the MBH may play a role in the modulation of the diurnal scheduling of ingestive behaviour in the rat.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Neuronal cholecystokinin-like immunoreactivity is postprandially released from primate hypothalamus.

By use of the push-pull perfusion technique, release of neuronal cholecystokinin-like immunoreactivity (CCK-LI) from hypothalamus of owl monkeys was investigated in relation to an intragastric meal. In overnight fasted, halothane-anesthetized owl monkeys, levels of CCK-LI in the hypothalamic push-pull perfusate were below assay sensitivity (less than 4 pg/30 min). After intragastric administration of a carbohydrate/amino acid meal, however, a 10-fold increase in CCK-LI release (51 +/- 7 pg/30 min) was observed in 5 out of 15 perfusion sites during the first postprandial 30 min. During the subsequent two 30-min intervals, release of CCK-LI was still increased with 32 +/- 5 pg/30 min and 15 +/- 6 pg/30 min, respectively. Thereafter, CCK-LI release was below assay sensitivity again. Addition of 40 mM potassium chloride (KCl) to the perfusion solution, which causes neuronal depolarization, resulted in a second increase in CCK-LI release of 56 +/- 7 pg/30 min which was comparable to the meal-induced release. All sites that exhibited an increase in CCK-LI were located in the anterolateral aspect of the hypothalamus. In experiments without meal-induced release, KCl did not have any effect on CCK-LI in perfusate, suggesting that these particular sites did not contain CCK-releasing terminals. High performance liquid chromatography (HPLC) identified the C-terminal octapeptide of CCK (CCK-8) as the predominant molecular form of CCK within the owl monkey hypothalamus. No gastrin-17 was present.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Noradrenergic regulation of cytosol estrogen receptors in female rat hypothalamus: possible role of alpha 2-noradrenergic receptors.

Because of the previous work demonstrating that the alpha 1-noradrenergic receptor antagonist, prazosin, decreases the concentration of cytosol estrogen receptors in rat mediobasal hypothalamus, a series of experiments was performed to determine the specificity of this effect to the alpha 1-noradrenergic system. Injection of the alpha 2-noradrenergic antagonist, yohimbine, caused a decrease in the concentration of estrogen receptors in mediobasal hypothalamus. In addition, the down-regulation of cytosol estrogen receptors by either the alpha 1-noradrenergic antagonist, prazosin, or the alpha 2-noradrenergic antagonist, yohimbine, could be blocked by pretreatment with the alpha 2-noradrenergic agonist, clonidine. The alpha 1-noradrenergic agonist, phenylephrine, was ineffective in blocking the effects of the alpha 1-noradrenergic antagonist, prazosin. These results add further support to the hypothesis that the alpha-noradrenergic system modulates the concentration of cytosol estrogen receptors in the rat hypothalamus. They suggest that the modulation may occur by way of alpha 2-noradrenergic receptors in addition to, or instead of, alpha 1-noradrenergic receptors.

Animals↗
PubMed1987

Olfactory bulb removal decreases androgen receptor binding in amygdala and hypothalamus and disrupts masculine sexual behavior.

In these experiments we examined the relationship between olfactory bulb removal, limbic system androgen receptor binding and male copulatory behavior. Sexually experienced male rats were castrated, and implanted with two 10 mm testosterone-filled silastic capsules. Animals then underwent either bilateral olfactory bulb removal (BOB) or sham surgery (Sham). Beginning 1-2 days postoperatively both BOB and Sham operates were given 4 tests for male copulation on alternate days. Less than 40% of BOB males ejaculated. In contrast, 80-100% of sham operates continued to ejaculate throughout the 4 postoperative tests. Cell nuclear androgen receptor binding was assessed in amygdala, hypothalamus, preoptic area and septum 1-2 and 8-9 days after either bulbectomy or sham surgery. We found that olfactory bulbectomy significantly reduces androgen receptor binding in amygdala and hypothalamus. The reduction in androgen receptor binding in amygdala occurs within 1-2 days following olfactory bulb removal and is correlated with the disruption of ejaculatory activity. These data suggest that the neuromodulation by olfactory bulb input to androgen-concentrating neurons in the amygdala and hypothalamus is necessary for effective copulation in male rats.

Amygdala↗
PubMed1988

Increased expression of alpha 1-adrenergic receptors in the hypothalamus of spontaneously hypertensive rats.

The specificity and molecular weights of alpha 1-adrenergic receptors in various tissues of spontaneously hypertensive (SH) rat were compared with normotensive controls (Wistar-Kyoto; WKY) with the use of [125I]HEAT and [125I]azidoprazosin, specific alpha 1-adrenergic receptor antagonists. Binding of [125I]HEAT to membranes prepared from SH rat brain hypothalamus was significantly higher, due to a 75% increase in the Bmax, than the WKY control. In contrast, the Bmax and Kd of [125I]HEAT binding to brainstem and liver membranes from SH rats were not significantly different from those of WKY controls. Competition-inhibition data suggested similar pharmacological specificity with potencies in the order of prazosin greater than yohimbine greater than propranolol for both WKY and SH rat membranes prepared from liver, hypothalamus, brainstem and neuronal cultures. Photoaffinity labeling of alpha 1-adrenergic receptors from hypothalamus, brainstem and neuronal cultures using [125I]azidoprazosin followed by SDS-PAGE and autoradiography showed the presence of one major band with a molecular weight (MW) of 105,000 Da for both WKY and SH rats. In contrast, labeling of liver alpha 1-adrenergic receptors revealed one major band with a MW of 60,000 Da. Quantitation of the 105,000-Da band from SH rat hypothalamic membranes demonstrated a 52% higher intensity compared with WKY controls. Neuronal cultures prepared from 1-day-old SH rats showed a similarly greater intensity of the 105,000-Da band compared with WKY controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Reduction of insulin binding in the arcuate nucleus of the rat hypothalamus after 6-hydroxydopamine treatment.

Insulin receptors are present in the hypothalamus, but the cell types bearing them are unknown. In order to test the hypothesis that some insulin receptors in the hypothalamus are associated with catecholamine terminals, rats were injected with 50 micrograms or 75 micrograms doses (intracerebroventricular) of 6-hydroxydopamine (6-OHDA). Control rats received vehicle only. The animals were sacrificed 7 days after injection, and catecholamine and indolamine levels in the hypothalamus were measured by high performance liquid chromatography with electrochemical detection. Localization of specific binding sites for [125I]-insulin in the arcuate (ARC), dorsomedial (DMN) and ventromedial (VMN) nuclei were determined by quantitative film autoradiography. Treatment with 6-OHDA resulted in a 70% reduction in hypothalamic norepinephrine content as compared to vehicle-treated controls (P less than 0.01). A slight depletion of epinephrine, dopamine and indolamines was also detected. Computerized image analysis of the autoradiograms was used to determine radioactivity bound (DPM/mm2) in each nucleus. Highest binding was in the ARC and DMN, with much lower binding in the VMN. Insulin binding in the ARC of the 6-OHDA-treated group was decreased by 25% compared to controls (P less than 0.01). No significant change in insulin binding was observed in the DMN or VMN. The 6-OHDA treatment had no significant effect on weight gain or on plasma insulin levels. The reduction of insulin binding in the ARC after 6-OHDA treatment supports the hypothesis that some insulin binding sites are located on catecholamine terminals in the arcuate nucleus.

Animals↗
PubMed1989

Neurally mediated cardiovascular responses to stimulation of cell bodies in the hypothalamus of the rat.

To study the cardiovascular responses to selective activation of neuronal cell bodies in the hypothalamus, DL-homocysteate (5-50 nl of a 0.15-M solution, pH 7.4) was injected into 417 histologically verified sites in the hypothalamus of 46 urethan-anesthetized, paralyzed and artificially ventilated rats. Injections resulted in depressor responses (-5 to -32 mm Hg) in 271 sites, in pressor responses (5-47 mm Hg) in 77 sites and 69 sites were not responsive. Depressor effects had a shorter latency (85% started within 5 s) than pressor effects (42% started within 5 s). Control injections of 0.15 M NaCl into 126 of the responsive sites were ineffective. Arterial pressure (AP) responses showed a positive correlation (r = 0.61, P less than 0.001) with changes in heart rate (HR). Analysis of the anatomical distribution of responsive sites showed that in all hypothalamic subdivisions depressor responses predominated except in the paraventricular nucleus, where mainly pressor effects and tachycardia were elicited. These results demonstrate that excitation of cell bodies in most hypothalamic regions elicits neurally mediated changes in AP and HR and that the traditional functional division of the hypothalamus into a rostral depressor and a caudal pressor area is probably based on the combined excitation of fibers of passage and cell bodies.

Animals↗
PubMed1989

Evidence that short photoperiod-induced gonadal regression in the Mongolian gerbil is mediated by the action of melatonin in the medial hypothalamus.

The present study was undertaken to examine the effects of exposure to short photoperiod (SD) and treatment with subcutaneous (s.c.) or intrahypothalamic melatonin-containing beeswax implants on reproduction in the Mongolian gerbil Meriones unguiculatus. Exposure of adult female gerbils to SD (8 h light: 16 h dark) caused a significant decrease in weight of the reproductive tract (ovaries, oviducts, uterus and vagina; RTW) compared to animals maintained under stimulatory photoperiod (12 h light: 12 h dark; 81.4 +/- 8.0 mg vs 151.8 +/- 16.0 mg, respectively (P less than 0.01]. Treatment with two large s.c. implants, each containing 3 mg melatonin, mimicked the antigonadal effect of SD (68.7 +/- 3.9 mg vs 118.1 +/- 19.5 mg for the blank (melatonin-free) implant controls; P less than 0.05). Gerbils with a small melatonin-beeswax pellet (containing 0.2 mg melatonin) in the anterior hypothalamus (AH) underwent a significant reduction in RTW compared to gerbils with a blank intrahypothalamic implant (73.0 +/- 5.7 mg vs 134.6 +/- 14.5 mg, respectively; P less than 0.01). Melatonin pellets in the mediobasal hypothalamus (MBH) also induced gonadal regression, but to a lesser degree (88.7 +/- 12.6 mg; P less than 0.05 vs blank controls). Small melatonin pellets placed elsewhere in the hypothalamus or s.c. had little effect on RTW (143.4 +/- 20.9 mg and 129.2 +/- 19.7 mg, respectively). Only 25% of the gerbils with melatonin pellet in the AH or MBH had a corpus luteum compared to 73% of the blank controls (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗