The CRF-related peptide sauvagine stimulates and the GABAB receptor agonist baclofen inhibits cyclic-AMP production in melanotrope cells of Xenopus laevis.
Release of alpha-MSH from the pars intermedia melanotrope cells of Xenopus laevis is regulated by various classical neurotransmitters and neuropeptides. We have examined the effect of two of these regulatory substances, the neurotransmitter GABA and the CRF-related peptide sauvagine, on the adenylate cyclase system of the melanotrope cells. Sauvagine treatment, which stimulates alpha-MSH release, lead to an elevation in the level of cyclic-AMP, an effect which was potentiated by cholera toxin. Treatment with baclofen, a GABAB receptor agonist, gave a pertussis toxin-sensitive decrease in the cyclic-AMP level and an inhibition of alpha-MSH release. We conclude that sauvagine stimulates alpha-MSH secretion through activation of adenylate cyclase and that GABAB receptor activation inhibits secretion through inhibition of cyclic-AMP production. Baclofen treatment sensitized melanotrope cells to the stimulatory action of 8-bromo-cyclic-AMP on the secretion of alpha-MSH. This observation supports the conclusion that GABAB receptor activation inhibits cyclic-AMP production.
Jenks
B G
BG
Department of Animal Physiology, University of Nijmegen, The Netherlands.
van Zoest
I D
ID
de Koning
H P
HP
Leenders
H J
HJ
Roubos
E W
EW
D000262:Adenylyl Cyclases / Q000502:physiology; D029845:Amphibian Proteins; D000818:Animals; D001418:Baclofen / Q000494:pharmacology*; D000242:Cyclic AMP / Q000096:biosynthesis* / Q000378:metabolism / Q000494:pharmacology; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism; D036361:Peptide Hormones; D010455:Peptides / Q000494:pharmacology*; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011963:Receptors, GABA-A / Q000502:physiology*; D013268:Stimulation, Chemical; D014665:Vasodilator Agents / Q000494:pharmacology*; D014981:Xenopus / Q000378:metabolism; D000521:alpha-MSH / Q000378:metabolism
D029845:Amphibian Proteins; D036361:Peptide Hormones; D010455:Peptides; D011963:Receptors, GABA-A; D014665:Vasodilator Agents; D000521:alpha-MSH; C025727:sauvagine; D009074:Melanocyte-Stimulating Hormones; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D001418:Baclofen