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Identification of a GABA-activated chloride-mediated synaptic potential in rat pars intermedia
P J Williams1, B A MacVicar, Q J Pittman
1Neuroscience Research Group, Faculty of Medicine, University of Calgary, Alta. (Canada).
Abstract:
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.