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      Differential Effects of Dopamine Agonists and Haloperidol on Release of Prolactin, Thyroid Stimulating Hormone, Growth Hormone and Luteinizing Hormone in Rats

      , , ,

      Neuroendocrinology

      S. Karger AG

      GH, LH, Male rats, Apomorphine, Piribedil, Haloperidol, PRL, TSH

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          Abstract

          The dose-response effects of apomorphine and ET-495 (piribedil), 2 specific dopamine (DA) receptor stimulators, and haloperidol, a DA receptor blocker, were tested on the secretion of prolactin (PRL), thyroid stimulating hormone (TSH), growth hormone (GH) and luteinizing hormone (LH) in male rats. Both apomorphine and piribedil reduced serum PRL and TSH levels, stimulated GH release at low but not at high doses and either had no effect or tended to reduce serum LH levels. The minimal effective dose of apomorphine for reducing PRL by 30 min was 0.01 mg/kg; TSH inhibition was observed with a dose of 0.1–0.3 mg/kg. The inhibitory effects of apomorphine (1.0 mg/kg) on PRL and TSH levels were maximal by 15 min and diminished by 120 min; plasma GH was highest 120 min after injection. Thyroidectomy (10 days) markedly elevated serum TSH, had no effect on serum PRL and inhibited the ability of apomorphine (0.1 or 0.3 mg/kg) to reduce TSH but not PRL levels. These observations may indicate that separate dopaminergic control mechanisms exist for TSH and PRL secretion. Administration of haloperidol elevated serum PRL, tended to lower TSH, dramatically reduced GH and had no effect on LH levels. Haloperidol pre-treatment blocked the effects of apomorphine on PRL, TSH and GH secretion. The overall results of this study indicate that DA agonists inhibit PRL and TSH, stimulate GH but do not stimulate LH release in male rats.

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          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1976
          1976
          20 March 2008
          : 20
          : 2
          : 121-135
          Affiliations
          Departments of Physiology and Pharmacology, Michigan State University, East Lansing, Mich.
          Article
          122476 Neuroendocrinology 1976;20:121–135
          10.1159/000122476
          958594
          © 1976 S. Karger AG, Basel

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          Pages: 15
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