Identification of a GABA-activated chloride-mediated synaptic potential in rat pars intermedia.
Intracellular recordings from melanotrophs in acutely isolated, intact pituitaries revealed inhibitory postsynaptic potentials (IPSPs) resulting from both pituitary stalk stimulation and exogenous gamma-aminobutyric acid (GABA) application. The stalk-stimulated and GABA-evoked IPSPs displayed identical conductance increases to chloride ions. Both responses reversed in polarity at the same membrane potential and were blocked with bicuculline, a GABAA antagonist. We conclude that activation of this synapse releases GABA which acts on a classical GABAA receptor to increase conductance to chloride in the melanotroph.
Williams
P J
PJ
Neuroscience Research Group, Faculty of Medicine, University of Calgary, Alta. (Canada).
MacVicar
B A
BA
Pittman
Q J
QJ
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002712:Chlorides / Q000502:physiology*; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D009433:Neural Inhibition; D010902:Pituitary Gland / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology*
D002712:Chlorides; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline