IN VIVO EFFECTS OF DOPAMINE AND DOPAMINERGIC ANTAGONISTS ON TESTICULAR MATURATION IN THE RED SWAMP CRAYFISH, PROCAMBARUS CLARKII

摘要

In vivo, dopamine (DA) inhibits testicular maturation in the red swamp crayfish, Procambarus clarkii. Crayfish given DA injections had a smaller testicular index, smaller testicular lobes, fewer mature sperm, and less-well-developed androgenic glands than did the control crayfish given physiological saline. Males administered 5-hydroxytryptamine (5-HT) or a DA receptor blocker, spiperone or pimozide, showed enhanced testicular maturation and more highly developed androgenic glands than did the control crayfish. When equimolar amounts of 5-HT and DA were co-injected, the actions of DA and 5-HT were found to be antagonistic. These results can be explained by assuming not only that 5-HT triggers release of the gonad-stimulating hormone (GSH) but that DA (a) triggers release of the gonad-inhibiting hormone (GIH), (b) inhibits GSH release, or (c) does both (a) and (b), with GSH and GIH affecting the androgenic glands directly, thereby regulating release of the androgenic gland hormone that has the well-established role of stimulating testicular maturation and spermatogenesis.