Dopamine (D2) or gamma-aminobutyric acid (GABAB) receptor activation hyperpolarizes rat melanotrophs and pertussis toxin blocks these responses and the accompanying fall in [Ca2+]i.
The effects, on membrane potential, of dopamine (DA) and gamma-aminobutyric acid (GABA), transmitters present in the secreto-inhibitor innervation to the melanotrophs, were monitored in primary cultures of rat melanotrophs with bis-oxonol. DA and GABA, acting through D2 and GABAB receptors, hyperpolarized the melanotrophs. Hyperpolarization was not suppressed by tetrodotoxin but was prevented by pertussis toxin and may thus be due to a G protein mediated mechanism. Pertussis toxin also blocked the effects mediated by the two receptors to reduce intracellular free Ca2+ ([Ca2+]i).
Taraskevich
P S
PS
Yale University School of Medicine, Department of Pharmacology, New Haven, CT 06510.
Douglas
W W
WW
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D037342:Pertussis Toxin; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D011954:Receptors, Dopamine / Q000187:drug effects / Q000502:physiology*; D017448:Receptors, Dopamine D2; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D011963:Receptors, GABA-A; D010566:Virulence Factors, Bordetella; D005680:gamma-Aminobutyric Acid; D037342:Pertussis Toxin; D002118:Calcium; D004298:Dopamine