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Results for “PITUITARY HORMONES”

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At least 523 records · Page 29Linked to original sources
PubMed1984

Effect of clonidine on the secretion of anterior pituitary hormones in heroin addicts and normal volunteers.

Neuroendocrine effects of intravenous injections of clonidine, 0.15 mg, were investigated in 13 heroin addicts and 14 normal control subjects. The study was designed to determine whether continuous opiate administration leads to the development of hypersensitive alpha 2-adrenergic receptors. The peak increments in levels of plasma growth hormone (GH) and beta-endorphin induced by clonidine did not differ between heroin addicts and normal control subjects. At no time interval could the clonidine-induced rise in GH levels in addicts be differentiated from that induced by placebo. Clonidine failed to alter plasma prolactin, gonadotropin, or thyrotropin levels in either heroin addicts or controls. Since clonidine's neuroendocrine effects are reportedly due to the activation of postsynaptic alpha 2-adrenoceptors, it appears that (1) continuous opiate use does not lead to the development of hypersensitive alpha 2-adrenergic receptors involved in neuroendocrine mechanisms and (2) brain norepinephrine does not play a role in the regulation of tonic prolactin, gonadotropin, and thyrotropin secretion in man.

Adolescent↗
PubMed1983

Interaction of atropine with naloxone to alter anterior pituitary hormone secretion.

The effects of third ventricular injection of naloxone and atropine, alone and together, on plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), growth hormone (GH), and thyroid-stimulating hormone (TSH) were studied in conscious, ovariectomized (OVX) rats. Samples were removed from unrestrained rats that had been previously implanted with an atrial cannula, and plasma hormone levels were determined by radioimmunoassay. Intraventricular injection of naloxone (30 micrograms) induced increases in plasma LH and GH concentrations, decreased plasma PRL levels, but did not alter plasma TSH. When atropine (100 micrograms) was injected intraventricularly, there was a decrease in plasma LH and an increase in PRL levels but no alterations in the levels of the other hormones. The action of naloxone on PRL and GH release was eliminated by simultaneous administration of atropine, but there was only a slight reduction in its effect on LH. The results indicate that central cholinergic neurons may play an important role, via muscarinic type receptors, in mediation of the effects of naloxone and presumably opiates on PRL and GH release, whereas the effects on LH appear to proceed independently of cholinergic neurons.

Animals↗
PubMed1985

Effects of intrahypothalamic injection of quinolinic acid on anterior pituitary hormone secretion in the unanesthetized rat.

Bilateral intrahypothalamic injections of the brain metabolite quinolinic acid (QUIN) were made in an attempt to examine its effects on the secretion of LH, PRL, GH and TSH. Quin, a neuroexcitatory amino acid with close structural similarities to glutamate, kainate and N-methylaspartate, was infused into unanesthetized male rats, the animals sacrificed 7.5 min later, and serum hormone concentrations determined by radioimmunoassay. QUIN caused surges in LH, PRL and GH release (316, 607 and 1,134% of control, respectively, at 50 micrograms QUIN) without affecting the serum concentrations of TSH. At lower doses, a preferential effect of QUIN on PRL release was observed. All QUIN-induced hormonal changes were inhibited by concomitant administration of the specific antagonist (-)-2-amino-7-phosphonoheptanoic acid, indicating the presence of QUIN-sensitive receptors on neurons which are intimately associated with endocrine regulation. Moreover, because QUIN-treated animals exhibited behavioral signs of seizure activity and neuroendocrine dysfunction has been reported to occur in human convulsive disorders, the data are also of interest in view of a possible mechanistic link between epileptic phenomena and hormone secretion.

Animals↗
PubMed1985

The effects of hypophysectomy and administration of pituitary hormones on luteal function and uptake of high density lipoproteins by luteinized ovaries and adrenals of the rat.

The role of plasma lipoproteins and hypophyseal hormones in the maintenance of progesterone secretion by the rat corpus luteum was investigated. In the first experiment, rats were treated daily from days 1-6 of pregnancy with 5 mg/kg 4-aminopyrozolopyramidine (4APP), a blocker of hepatic lipoprotein secretion, or with 5 mg/kg 4APP and 1 or 2 mg ovine PRL or 0.1 ml 0.5% phosphoric acid (4APP vehicle). The administration of 4APP reduced serum cholesterol and progesterone levels on days 2-6 of pregnancy and ovarian progesterone on day 6. The reduced progesterone secretion had no effect on embryo implantation. PRL, in the doses used, was incapable of abrogating the effects of 4APP on circulating or ovarian progesterone levels. Ovaries and adrenals, but not kidneys, of pseudopregnant rats exhibited specific and saturable uptake of porcine high density lipoprotein (HDL). Time-course studies indicated that the uptake of HDL was rapid in ovaries compared to that in adrenals. Ovaries from rats not only exhibited uptake of porcine HDL, but also were capable of using it for progesterone synthesis. Immature rats were assigned to 7 groups of 16 rats each; 8 rats from each group received 4 mg/kg 4APP, and 8 received 4APP vehicle from day 1 of pseudopregnancy. Four groups underwent hypophysectomy on day 1 and received one of the following: 0.1 mg (30 IU/mg) ovine PRL, 0.1 mg ovine LH or 0.1 mg synthetic ACTH daily, or no replacement therapy. Three sham-hypophysectomized groups received 0.1 mg PRL or LH twice daily or no hormone treatment. On day 5 of pseudopregnancy, rats received intravascular HDL, as described above, and were killed 1 h later. Treatment with 4APP increased the adrenal uptake of HDL, but ovarian uptake was not different from that in the control group. Hypophysectomy reduced both adrenal and ovarian uptake of HDL. In adrenals only ACTH at the dose employed ameliorated reduction of HDL uptake induced by hypophysectomy, while in the ovaries, both PRL and LH reversed the effect of hypophysectomy. The effect of PRL on uptake was specific to [125I]HDL and did not alter [125I]albumin uptake. It is concluded that: 1) hypophysectomy reduces HDL uptake in the luteinized rat ovary; and 2) PRL and LH replacement therapy maintain ovarian uptake of HDL, suggesting a direct effect of these luteotropins on lipoprotein uptake.

Adrenal Glands↗