Adrenergic and dopaminergic regulation of gonadotropin-releasing hormone release from goldfish preoptic-anterior hypothalamus and pituitary in vitro.
The involvement of adrenergic and dopaminergic receptor subtypes on in vitro release of radioimmunoassayable gonadotropin-releasing hormone (GnRH) from incubated preoptic-anterior hypothalamic (P-AH) slices and pituitary fragments of sexually mature male goldfish was studied. Norepinephrine (NE) produced a dose-related stimulation of GnRH from P-AH slices, but not from pituitary fragments. The effects of some adrenergic receptor agonists (1 microM) on GnRH release from P-AH slices were tested: phenylephrine (alpha 1-agonist) significantly stimulated GnRH release; clonidine (alpha 2-agonist) and isoproterenol (beta-agonist) were ineffective. Incubation of P-AH slices with phentolamine (alpha 1/alpha 2-antagonist) and prazosin (alpha 1-antagonist), at a concentration of 1 microM, inhibited the release of GnRH induced by NE (60 microM); the alpha 2-antagonist yombibin and the beta-antagonist propanolol were ineffective. None of the adrenergic antagonists (1 microM) tested produced significant effects on spontaneous release of GnRH from both tissue preparations. Spontaneous release of GnRH from both P-AH slices and pituitary fragments was reduced by dopamine (DA) in a dose-related manner. The effects of some DA agonists (1 microM) were tested: apomorphine (D1/D2-agonist) and SKF 38398 (D1-agonist), but not bromocriptine and LY-171555 (D2-agonists) significantly reduced spontaneous GnRH release from P-AH slices in vitro. On the other hand, D2-agonists, but not D1-agonists, significantly reduced GnRH release from pituitary fragments. The effects of DA antagonists (1 microM) were also tested: in P-AH slices, addition of SKF-83566 (D1-antagonist) significantly reduced spontaneous GnRH release; pimozide and domperidone (D2-antagonist) were ineffective when tested alone.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Zoology, University of Alberta, Edmonton, Canada.
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Peter
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D015259:Dopamine Agents / Q000494:pharmacology; D018492:Dopamine Antagonists; D006054:Goldfish; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007032:Hypothalamus, Anterior / Q000378:metabolism*; D010902:Pituitary Gland / Q000378:metabolism*; D011941:Receptors, Adrenergic / Q000502:physiology*; D011954:Receptors, Dopamine / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D015259:Dopamine Agents; D018492:Dopamine Antagonists; D011941:Receptors, Adrenergic; D011954:Receptors, Dopamine; D007987:Gonadotropin-Releasing Hormone