Electrophysiological study with K+- and Ca2+-sensitive micropipettes of GABA receptors in the rat neurointermediate lobe in vitro.
An efflux of K+ and a decrease in extracellular Ca2+ activity are to be expected when GABA markedly depolarizes the membrane of unmyelinated axons or secretory cells. Accordingly, we used extracellular recordings of ionic movements to specify GABA receptor presence in parts of the pituitary having GABAergic innervation: the neurohypophysis and intermediate lobe (NIL). We identified a site of action having the same desensitization characteristics and pharmacological criteria as the GABA A receptor which modulates Cl- -conductance. Baclofen, a GABA B agonist, was without effect. The possible distribution of receptors and role of GABAergic synapses in modulating neurotransmitter and hormone release by the NIL are discussed.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D005260:Female; D007473:Ion Channels / Q000502:physiology; D008297:Male; D008564:Membrane Potentials; D009115:Muridae; D009412:Nerve Fibers / Q000502:physiology; D010904:Pituitary Gland, Posterior / Q000294:innervation*; D011188:Potassium / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000502:physiology*; D011963:Receptors, GABA-A; D009435:Synaptic Transmission
D007473:Ion Channels; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D011188:Potassium; D002118:Calcium