Margaret F Menadue

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GH and PRL levels were measured by RIA in plasma samples taken from genetically obese and nonobese rats over a 6-h period at consecutive 15-min intervals. The mean GH level was 204 ng/ml for lean animals and 48 ng/ml for obese rats; the difference is significant (t = 5.8; P less than 0.01). For the group of 5 lean rats, there were 10 GH peaks that exceeded(More)
Human growth hormone (hGH) was administered to chronically cannulated male rats and its effect upon the physiological secretory patterns of rat growth hormone (rGH) and prolactin were observed. In comparison with injected control animals, a reduction in the size of spontaneous secretory bursts of rGH was apparent when hormone concentrations were compared(More)
Medio-basal hypothalamic (MBH) catecholamine mechanisms in the regulation of prolactin and growth hormone (GH) secretion were investigated in unanesthetized rats with chronic indwelling venous cannulae and bilateral MBH directed intracerebral guide cannulae. MBH injections of the catecholamine-specific neurotoxin 6-hydroxydopamine (6-OHDA; 2 micrograms base(More)
Localized intracerebral microinjections of GABA, muscimol, picrotoxin and bicuculline were made in the anterior and basal hypothalamus to determine possible sites of action of GABA in the regulation of prolactin and growth hormone (GH) secretion. Studies were carried out in unanesthetized male rats with chronic indwelling atrial cannulae and intracerebral(More)
Plasma growth hormone (GH) and prolactin concentrations were measured by radioimmunoassay in unanesthetized male rats after stereotaxic microinjection of adrenergic agents and 6-hydroxydopamine into the preoptic-anterior hypothalamic area (PO/AHA). Norepinephrine, epinephrine, isoprenaline and clonidine failed to stimulate GH, moreover, 16 nanomoles(More)
Spontaneous pulsatile growth hormone (GH) secretion and stress-induced suppression of GH was examined in chronically cannulated male rats with electrolytic lesions of the periventricular preoptic anterior hypothalamic area (PO/AHA) where somatostatin neurons innervating the median eminence are known to be located. Median eminence somatostatin was depleted(More)
BACKGROUND Amitraz, an insecticide used to prevent tick and mite infestation of cattle, crops and dogs, is an alpha2-adrenergic receptor agonist that inhibits GnRH release and the ovulatory LH surge in rats. Noradrenalin, the physiological ligand for adrenergic receptors, inhibits progesterone production by IVF-derived granulosa cells, but the effects of(More)
Prolactin concentrations were measured in plasma in unanaesthetized male rats chronically prepared with venous and intracerebral cannulae, before and after treatment with bilateral intracerebral injections of serotonin and fenfluramine. Serotonin 1, 5, and 10 nmol injected in the medial basal hypothalamus caused dose-related rises in prolactin(More)
In unanaesthetized rats chronically prepared with venous and intracerebral cannulae, noradrenaline injected into the region of the supraoptic nuclei caused a dose-dependent increase in plasma vasopressin, measured by radioimmunoassay. A similar response was obtained with phenylephrine, but not with either clonidine or isoprenaline. The secretion of(More)
1. Angiotensin (Ang) II causes cardiac hypertrophy in vitro and in vivo. It also stimulates the release of endothelin (ET)-1. Endothelin-1 induces hypertrophy of cardiomyocytes in vitro. 2. In the present study, we examined whether the cardiac hypertrophic action of AngII in vivo was mediated by ET-1 via ETA receptors. We also determined whether arginine(More)