title: On the mechanism of action of GABA in pelvic vesical ganglia: biphasic responses evoked by two opposing actions on membrane conductance.
abstract: Intracellular recording techniques were used to study the response of cat vesical pelvic ganglion neurones loaded with permeable anions to the application of GABA in vitro. In 106/127 neurones GABA evoked a biphasic response, the initial phase of which was depolarizing and associated with a conductance increase; the latter phase was hyperpolarizing and associated with a conductance decrease. The GABA evoked hyperpolarization and conductance decrease were related and behaved as though generated by closure of ion channels open in the resting membrane. The hyperpolarization had a strong inhibitory action on both spontaneous activity, and excitation evoked by depolarizing current injection and pre-synaptic nerve stimulation. Ion substitution experiments suggest that the conductance decrease is primarily to chloride ions, although other ionic species may contribute. Short iontophoretic applications of GABA-evoked monophasic depolarizing excitatory responses, even during the hyperpolarizing response evoked by perfusion of GABA, suggesting no cross-desensitization between the mechanisms generating the initial and late phases of the biphasic response.
mesh_terms: D000818:Animals; D002415:Cats; D002712:Chlorides / Q000378:metabolism; D005260:Female; D005726:Ganglia, Parasympathetic / Q000187:drug effects*; D005728:Ganglia, Sympathetic / Q000187:drug effects*; D007473:Ion Channels / Q000187:drug effects*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009433:Neural Inhibition / Q000187:drug effects; D009474:Neurons / Q000187:drug effects; D013569:Synapses / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects*; D001743:Urinary Bladder / Q000294:innervation*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D002712:Chlorides; D007473:Ion Channels; D005680:gamma-Aminobutyric Acid