Margaret F Menadue

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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)
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)
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)
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)
The role of preoptic/anterior hypothalamic area (PO/AHA) neurones in the regulation of basal patterns of growth hormone (GH) and prolactin (Prl) secretion was investigated in unanesthetized male rats prepared with chronic indwelling venous cannulae. PO/AHA injections of the neurotoxin kainic acid (KA) substantially reduced both GH and Prl secretion.(More)
Impaired regulation of salt and water balance in left ventricular dysfunction and heart failure can lead to pulmonary and peripheral edema and hyponatremia. Previous studies of disordered water regulation in heart failure have used models of low cardiac output with normal cardiac function (e.g., inferior vena cava ligation). We investigated thirst and(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 conscious rats, serotonin microinjected into the basal hypothalamus caused secretion of GH maximal within 10-25 min. The effects of serotonin on GH were blocked by the non-selective serotonin receptor blocker, metergoline 2.5 mg/kg, but not by the serotonin type 2 receptor blocker, ketanserine 0.2 mg/kg. Injections of serotonin in the preoptic/anterior(More)