title: Regulation of cyclic-AMP synthesis in amphibian melanotrope cells through catecholamine and GABA receptors.
abstract: Catecholamines and GABA are neurotransmitters involved in the regulation of release of pro-opiomelanocortin (POMC) derived peptides from the neurointermediate lobe of Xenopus laevis. The present study concerns the relation of these neurotransmitters to the adenylate cyclase system of the melanotrope cell. During in vitro incubation of isolated melanotrope cells it was found that dopamine, adrenaline and LY 171555 induced inhibition of forskolin-stimulated cAMP production and concomitantly inhibited MSH release. Activation of the GABAb receptors by baclofen also induced inhibition of cAMP production and alpha MSH secretion. Activation of the GABAa receptors evoked stimulation of cAMP production, while alpha MSH release was slightly inhibited, indicating that the GABAa mechanism may prove to be complex. A dual regulation through two subtypes of this receptor might be involved, one stimulating release through the adenylate cyclase system, while the other would inhibit secretion.
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D000242:Cyclic AMP / Q000096:biosynthesis*; D004298:Dopamine / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D004873:Ergolines / Q000494:pharmacology; D066298:In Vitro Techniques; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000378:metabolism*; D019257:Quinpirole; D011941:Receptors, Adrenergic / Q000187:drug effects / Q000378:metabolism*; D017983:Receptors, Catecholamine; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism*; D014982:Xenopus laevis / Q000502:physiology
chemical_list: D004873:Ergolines; D011941:Receptors, Adrenergic; D017983:Receptors, Catecholamine; D011963:Receptors, GABA-A; D019257:Quinpirole; D015124:8-Bromo Cyclic Adenosine Monophosphate; D009074:Melanocyte-Stimulating Hormones; D000242:Cyclic AMP; D004298:Dopamine; D004837:Epinephrine