Showing papers on "Hypothalamus published in 1973"

Hypothalamic Polypeptide That Inhibits the Secretion of Immunoreactive Pituitary Growth Hormone

Abstract: A peptide has been isolated from ovine hypothalamus which, at 1 x 10(-9)M, inhibits secretion in vitro of immunoreactive rat or human growth hormones and is similarly active in vivo in rats. Its structure is H-Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys-OH The synthetic replicate is biologically active.

Stimulation of Human Prolactin Secretion by Intravenous Infusion of L-Tryptophan

Abstract: Previous studies have demonstrated that the secretion of human prolactin is regulated primarily by factors that influence catecholamines of the hypothalamus. In an effort to identify other factors that may regulate prolactin secretion, the amino acid L-tryptophan, a precursor in the synthesis of serotonin, was infused into normal human volunteers. Intravenous infusion of L-tryptophan, 5-10 g over a 20 min period, but not equivalent amounts of 17 other amino acids, induced marked increases in serum prolactin concentrations in eight normal human volunteers. Increases of 20-200 ng/ml above the control level were observed with peak values at 20-45 min after initiation of the infusion. In addition, infusion of L-tryptophan was associated with decreases in serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyrotropin in those subjects in whom the base-line serum hormone concentration was above the lower limits of assay detectability. No consistent change was observed in serum concentrations of growth hormone, cortisol, or glucose. Four subjects with juvenile diabetes demonstrated increases in serum prolactin values comparable with those observed in healthy individuals in response to infusions of L-tryptophan. Serum prolactin values in patients with surgically induced hypopituitarism were undetectable or deficient after infusion of 10 g of L-tryptophan. In this respect, infusion of L-tryptophan was equally effective in these subjects as the standard chlorpromazine stimulation test in identifying patients with hypopituitarism, indicating that the infusion of L-tryptophan may serve as a sensitive and reliable clinical test of prolactin secretory reserve. Further studies relating to the possible mechanism of action of L-tryptophan indicated that infusion of 5-hydroxytryptophan represents a much more potent stimulus for the secretion of prolactin and that premedication with the serotonin antagonist, methysergide maleate, serves to blunt the effect of L-tryptophan on prolactin secretion. These results support the concept that the effect of L-tryptophan on the secretion of human prolactin is mediated through its conversion to serotonin and are consistent with reported experimental observations that serotonin may participate in the reciprocal regulation of prolactin and gonadotropins.

Participation of Serotonin-Containing Neurons in the Suckling-Induced Rise in Plasma Prolactin Levels in Lactating Rats

Abstract: Plasma prolactin levels were measured by radioimmuno-assay in free-moving lactating rats bearing heart cannulas. Litters adjusted to 6 pups were returned to the mothers after a separation of 8–12 h fr

Neuro-Endocrine Correlates of Immune Response

Abstract: Bilateral symmetrical electrolytic lesions were produced in the following areas of the rat brain: hypothalamus, reticular formation, thalamus, superior colliculus, caudate nucleus and amygdaloid compl

Effects of Serotonin Precursors and Melatonin on Serum Prolactin Release in Rats

Abstract: A single intravenous injection of tryptophane, 5-hydroxytryptophane, serotonin or melatonin was given to rats on the morning of proestrus and to hypophysectomized, pituitarygrafted female rats. The 5-hydroxytryptophane increased serum prolactin about 9 fold by 30 min after injection and about 6 fold by 1 hr after injection as compared to control values; it also doubled serum prolactin values in hypophysectomized rats with an anterior pituitary graft. Tryptophane approximately doubled serum prolactin over control values by 30 min and 2 hr after injection, but these differences were not significant statistically. Serotonin itself did not significantly alter serum prolactin levels, but melatonin significantly increased serum prolactin over control levels by 1 and 2 hr after injection. These results suggest that brain serotonin, its precursors and melatonin may have a role in stimulating prolactin release, and thereby serve to counter the inhibitory effects of hypothalamic catecholamines on prolactin release....

Autoradiographic localization of radioactivity in the rat brain after the injection of 1,2-3H-testosterone.

Abstract: The localization of radioactivity in the brain of immature intact and mature castrated Sprague—Dawley rats was investigated by drymount autoradiography at 1 hr after the injection of l,2–3H-testosterone. Radioactivity is found to be selectively concentrated and retained in specific neurons in the nucleus (n.) arcuatus and the n. ventromedialis hypothalami, the n. preopticus medialis, the n. interstitialis striae terminalis, the n. septi lateralis, the hippocampus and the amygdala. The topographic distribution of androgenconcentrating neurons agrees well with areas in the brain that have been associated with the regulation of gonadotropin secretion and male sex behavior. The autoradiographic data are consistent with the hypothesis that androgen feedback occurs at hypothalamic and extrahypothalamic sites in the central nervous system. (Endocrinology 92: 251, 1973)

Thyrotropin releasing hormone (TRH): neurotransmitter regulation of secretion by mouse hypothalamic tissue in vitro

Abstract: The regulation of thyrotropinreleasing hormone (TRH) secretion by putative neurotransmitters was studied in vitro by measuring the release of radioactive TRH from mouse hypothalamic fragments which had been pulselabelled with tritiated TRH precursor amino acids. Both dopamine and norepinephrine, when added to the incubation media in a concentration of 10-4M or 1O-5M, increased the release of 3H TRH. The TRH stimulatory effects of dopamine, but not of norepinephrine were abolished by Disulfiram, a β-oxidase inhibitor, thus suggesting that dopamine was effective after conversion to norepinephrine. Release of 3H-TRH was decreased upon addition of serotonin at 10-4M. Acetylcholine in the presence of either Eserine or the acetylcholine analogue, carbachol, had no effect on TRH release. These findings suggest that the regulation of TRH release is under a dual monoaminergic control system with a positive noradrenergic and a negative serotoninergic component. (Endocrinology 93: 626, 1973)

Neurons of the hypothalamus concentrate (3H)progesterone or its metabolites.

Abstract: Selective concentration of [ 1 H ] progesterone or its metabolites is observed in nuclei of neurons in certain hypothalamic regions of the guinea pig 15 minutes after injection of [ 1,2,6,7- 3 H ] progesterone, by use of dry-mount autoradiography. Highest concentrations of progestin target neurons exist in the nucleus arcuatus, the nucleus preopticus periventricularis, and the nucleus preopticus suprachiasmaticus. Previous administration of unlabeled progesterone inhibits the nuclear concentration of radioactivity, but cortisol has no effect. Estradiol priming enhances the nuclear uptake of radioactivity. The results demonstrate the existence of progestin target sites in the hypothalamus and suggest a direct action of progestin on certain hypothalamic structures.

Catecholamines in the Median Eminence: New Evidence for a Major Noradrenergic Input

Abstract: THE median eminence of the hypothalamus contains large amounts of hypothalamic hormones (releasing factors)1, but the cellular localization of these hormones is unknown. In contrast, there is convincing evidence, from fluorescence histochemical studies, for the existence of a dopaminergic system with neuronal cell bodies in the arcuate nucleus, whose axons project into the external layer of the median eminence2. Deafferentation studies combined with fluorescence3,4 or electron microscopy5 have suggested that there may also be a noradrenergic component in the innervation of the median eminence. We now report additional biochemical evidence supporting the existence of a substantial noradrenergic input to this brain area. We also describe the properties of a dopamine (DA) uptake system in the median eminence.

Inhibition of hypoglycemia-induced growth hormone secretion by the serotonin antagonists cyproheptadine and methysergide.

Abstract: Growth hormone secretion is provoked by hypoglycemia. Since hypothalamic serotonin content increases during insulin-induced hypoglycemia, the role of hypothalamic serotonin in growth hormone secretion in man was examined. Hypoglycemia-induced growth hormone release in normal volunteers was studied during a control period and after two days of administration of serotonin antagonists, cyproheptadine and methysergide. Plasma growth hormone was measured by radioimmunoassay, and total growth hormone secretion was expressed as the area under the growth hormone curve from 0 to 120 minutes. Cyproheptadine administration resulted in a 59 per cent reduction (p<0.01), and methysergide in a 35 per cent reduction (p<0.05) in growth hormone secretion. The decrease in plasma glucose during the control and treatment periods indicated a comparable stimulus for growth hormone release in both study groups. If these drugs act by antagonizing serotonin, as assumed, this study suggests that serotonin is involved in hy...

Twenty-four hour patterns of plasma luteinizing hormone and follicle-stimulating hormone in sexual precocity.

Abstract: To evaluate the secretory patterns of luteinizing and follicle-stimulating hormones in various forms of sexual precocity, plasma levels of these hormones were measured every 20 minutes for 24 hours in six patients and nine normal pubertal children. Three patients with "idiopathic" precocious puberty and one boy with a hypothalamic tumo rand precocious puberty exhibited fluctuating plasma concentrations that resembled findings in normal pubertal children in that they had significantly increased luteinizing hormone concentrations during sleep. Two boys with congenital adrenal hyperplasia and advanced bone age also showed episodic fluctuation of both hormones and augmented luteinizing hormone concentrations during sleep. These findings show that patients with precocious puberty related either to Central-nervous-system stimulation or to a primary adrenal disorder can exhibit the normal pubertal luteinizing hormone pattern of augmented secretory activity synchronous with sleep. (N Engl J Med 289:282–2...

A Comparison of the Pituitary Adrenal Activity Elicited by Electrical Stimulation of Preoptic, Amygdaloid and Hypothalamic Sites in the Rat Brain

Abstract: In rats anesthetized with pentobarbital, increments in corticosterone concentration were elicited upon electrical stimulation through chronically implanted electrodes. Prestimulation steroid levels were low. Poststimulation levels varied according to the site stimulated. These sites, ranging in order of responsiveness from greatest to least, were amygdala, mammillary hypothalamus, tuberal hypothalamus, and preoptic area. The corticosterone increments obtained under anesthesia were similar in magnitude to those obtained in the absence of anesthesia. Placement of the electrodes in the median eminence itself did not enhance the responsiveness. Hind leg shock evoked a steroid increment comparable to that produced by tuberal stimulation ; and ketamine, a centrally acting drug, provided an estimate of the maximal centrally elicited response. The evidence is consistent with the view that excitatory afferent paths to corticotropin releasing factor (CRF) neurons and the CRF neurons themselves lie distributed in the tissue stimulated.

Aromatization in the central nervous system of rabbits: effects of castration and hormone treatment.

Abstract: In vitro incubation of tissue homogenates from the hypothalamus and limbic system of adult male and female rabbits with A4 androstene- 3-17-dione-7-3H resulted in the formation of tritium-labeled estrone. There was no measurable conversion by the pituitary gland, olfactory lobes and cerebral cortex. Activity was primarily localized in the anterior hypothalamus. While in female rabbits the amount of limbic activity was equal to that in the hypothalamus, in males the hypothalamus was more active than the limbic system. Addition of large amounts of nonradioactive estrone to the incubation had no dramatic or consistent effect on aromatization. There was a significant sex difference in hypothalamic activity; the male being three times as active as the female (p > 0.02). The aromatizing activity in male limbic system was consistently higher than in the female. The sex difference in the hypothalamus was diminished by chronic castration as a result of a markedly increased activity in both sexes. The limbic system...

Reproductive Endocrinology of Fishes

Abstract: While evidence is currently lacking for the agnatha and elasmobranchs, the release of pituitary gonadotropin by the teleost pituitary appears to be under stimulatory control by the hypothalamus. Gonadotropin has to date only been purified from teleost pituitary glands. Bioassay and biochemical data suggest that the teleost pituitary gland elaborates only one gonadotropin; however, there is some conflicting histological data on this point. Salmon gonadotropin has a molecular weight of approximately 29,000 at neutral p H and approximately 13,000 at low p H or after treatment with 8m urea or 1m propionic acid. Radioimmunossays have recently been developed for carp and salmon gonadotropin. Immunological techniques have also been used to identify pituitary gonadotrops. Pharmacological treatment of fish with methallibure has permitted inhibition of gonadal development while treatment with clomiphene citrate has stimulated ovulation. The role of corticosteroids and other steroid hormones in ovulation is still not fully elucidated. It is possible that the control of ovulation may differ between species. Experiments are described which aim to enhance natural stocks of pink salmon by endocrine manipulation of sexual development in the male.

Nuclear receptor estrogen complex: accumulation, retention and localization in the hypothalamus and pituitary.

Abstract: The effect of estradiol injection on the quantity of estrogen receptors in the nuclear fraction of the hypothalamus and the anterior pituitary was examined by the 3H-estradiol exchange assay. The accumulation of the receptor estradiol complex (RE) in the nuclear fraction of both tissues in the female rat reached a maximum one hour after an injection of 25 μg of estradiol. Between 1 and 12 hr after treatment, parallel declines in hypothalamic and hypophyseal nuclear RE were observed. The quantity of receptor in the pituitary is several-fold greater than the quantity in the hypothalamus. However, hypothalamic receptors are confined to the basal medial region, and the concentration in this region (1.1 fmole/μg DNA) is similar to the concentration in the pituitary (1.3 fmole/μg DNA). The increases in nuclear RE in both tissues are equally dependent on the quantity of estrogen administered. One hr after an injection of a physiological dose (0.5 μg) of estradiol the amount of receptor in the nuclei in both tiss...

A new hypothalamic pathway to the median eminence containing neurophysin and its hypertrophy in sheep with natural scrapie.

Abstract: THE hypothalamus is linked to the pituitary by two anatomically distinct neuronal neurosecretory pathways. The first, the hypothalamo-distal neurohypophysial system, commonly termed the supraoptico-neurohypophysial system (SNHS), arises in the “magno-cellular” cell bodies of the supraoptic nuclei (SON) and the paraventricular nuclei (PVN), whence their large axons descend via the internal infundibular zone to the posterior pituitary (Fig. 1)1,2. This system is characterized immunochemically by the neurophysins, the specific carrier-proteins for vasopressin and oxytocin3–6.

Neuroendocrinology of Teleosts

Abstract: The nucleus preopticus has been shown to receive afferent input from certain cranial nerves and the spinal cord. In addition, the nucleus preopticus and its tracts can synthesize and transport hormones about as rapidly as a mammal can. The nucleus preopticus is functionally involved in the spawning reflex behavior. The hypothalamic control of each of the adenohypophysial hormones is discussed. There is conflicting and incomplete evidence for the control of melanocyte-stimulating hormone (MSH), prolactin, and somatotropin. Secretion of prolactin and MSH may each be controlled by an inhibitory factor. Corticotropin secretion has been shown to be controlled by corticotropin releasing factor (CRF). There is a negative fedback effect by cortisol on the pituitary to suppress corticotropin secretion. Gonadotropin secretion is controlled by gonadotropin releasing factor (GRF). A part of the nucleus lateralis tuberis is involved in the control of gonadotropin secretion. A great deal of indirect evidence indicates that a thyrotropin inhibitory factor (TIF) controls thyrotropin secretion. There is a negative feedback effect by thyroxine on the pituitary to suppress thyrotropin secretion and a positive feedback effect on the hypothalamus to stimulate TIF secretion. The above findings are restricted to only one or two species in each instance. It is not known how general the above mechanisms of control are found throughout the teleosts.

The effect of catecholamines on hormone release from anterior pituitaries and ventral hypothalami incubated in vitro.

Abstract: Incubation of pituitaries in the presence of cate-cholamines produced a dramatic inhibition of prolactin release by the glands. The minimal effective dose of both dopamine hydrochloride (DA) and norep

Reduced pressor responses to stimulation of the locus coeruleus after lesion of the posterior hypothalamus.

Abstract: Electrical stimulation of the locus coeruleus or of the hypothalamic posterior area of cats under pentobarbitone anaesthesia elicited a rise of the arterial blood pressure. Electrocoagulation of the hypothalamic posterior area or its lesion by the injection of ethanol significantly diminished the pressor response to electrical stimulation of the locus coeruleus. The pressor response to electrical stimulation of the area posterior was almost completely abolished after electro-coagulation and strongly inhibited after injection of ethanol. It is suggested that adrenergic neurones ascending from the locus coeruleus to the posterior hypothalamus may be involved in the hypothalamic regulation of the arterial blood pressure.

The Nature of Estrogen and Prolactin Effect on Mammary Tumorigenesis

Abstract: Increased release of pituitary prolactin as a result of placement of electrolytic lesions in the median eminence of the hypothalamus greatly accelerated the growth rate of carcinogen-induced mammary tumors in rats. Ovariectomy in these rats induced a rapid regression of tumors in spite of high plasma levels of prolactin. Grafting a pair of ovaries into ovariectomized rats with lesions of the median eminence did not alter the levels of plasma prolactin, but it did cause a rapid resumption of tumor growth. It is concluded that the prolactin stimulus to growth of mammary tumor is dependent on the presence of ovarian hormones.

Colonic motility in the cat. II. Extrinsic nervous control.

Abstract: Rostad. H. Colonic motility in the cat. III. Influence of hypothalamic and mesencephalic stimulation. Acta physiol. scand. 1973. 89. 104–115. Colonic motility recorded with sensitive extraluminal strain gage transducers was studied in lightly anesthetized cats following electrical stimulation of hypothalamic, and mesencephalic structures. Stimulation of various structures of the hypothalamus produced the following: 1) The sympatho-inhibitory area in the anterior hypothalamus increased colonic activity concomitantly with a fall in blood pressure. 2) The ventral anterior and lateral hypothalamus produced excitatory colonic effects, but these were usually associated with a rise in blood pressure. Similar effects were obtained from the dorsal part of the ventromedial hypothalamic nucleus. 3) Stimulation of the ventral part of the hypothalamus, mainly corresponding to the course of the medial forebrain bundle, and the ventral part of the ventromedial nucleus, resulted in inhibitory colonic effects. Stimulation of various structures of the mesencephalon produced the following: 1) The central gray substance, red nucleus and reticular substance elicited increased colonic effects, most conspicuous in the proximal part of the colon. These responses were usually associated with a blood pressure rise. 2) Points within the central tegmental tract and the medial lemniscus resulted in inhibition of colonic motility. The. functional significance of the results and their relation to behavioural patterns are discussed.

Effects of adrenergic drugs on pressor responses to hypothalamic stimulation.

Abstract: The posterior area of the hypothalamus of anaesthetized cats was superfused with artificial cerebrospinal fluid through a push-pull cannula. Electrical stimulation with the non-insulated tip of the cannula elicited a rise of the mean arterial blood pressure. Superfusion of the hypothalamic posterior area with tolazoline or piperoxan caused a dose-dependent inhibition of the pressor responses to electrical stimulation. Labelling of the posterior area with 3H-noradrenaline 2 h before the beginning of the superfusion showed that the inhibitory effect of tolazoline on the pressor responses was accompanied by an increased release of total radioactivity and an enhanced per cent release of 3H-noradrenaline, while that of its metabolites was reduced. Superfusion of the nucleus of the solitary tract with clonidine evoked a dose-dependent inhibition of the pressor responses to electrical stimulation of the ipsilateral hypothalamic posterior area. It is concluded that 1. Alpha-adrenoreceptors are present in the posterior hypothalamus and are involved in the blood pressure rise elicited by its electrical stimulation. 2. A feedback mechanism is present in the hypothalamus which regulates the release of noradrenaline and which is mediated by alpha-adrenoreceptors; inhibition of the regulation of the release of noradrenaline by alpha-adrenoreceptors blocking agents leads to an enhanced release of the neuro-transmitter. 3. Activation of the inhibitory pathways of the nucleus of the solitary tract by clonidine diminishes the pressor response to electrical stimulation of the hypothalamic posterior area. 4. Two adrenergic systems localized in different areas of the central nervous system oppose each other in their regulatory effects on arterial blood pressure.

Effects of angiotensin II on central neurons

Abstract: Effects of angiotensin II administered intravenously and by means of electrophoresis through multibarrel micropipette electrodes on the frequency of extracellularly recorded action potentials of brain cells were determined. A total of 293 neurons in seven different parts of the brains of male and female hooded rats anesthetized with urethan or a mixture of urethan and chloralose were tested. Results indicate that angiotensin affects many different cells within the lateral hypothalmus, zona incerta, ventromedial and dorsomedial hypothalamic nuclei, dentate gyrus and thalamus. The cells of the LH and zona incerta are the most sensitive to angiotensin and two types of lateral hypothalamic neurons were found which were affected differently by angiotensin and stimulation of the basolateral amygdaloid nucleus. Some of the Na sensitive neurons, all of which were sensitive to angiotensin, displayed a very pronounced potentiation of discharge frequency when angiotensin and Na were administered simultaneously. Angiotensin II might therefore influence drinking because of a relatively low threshold effect on hypothalamic neurons.