[The cross desensitization and modulation of Cl currents activated by gamma-aminobutyric acid and L-glutamate in the isolated neurons of Aplysia].

Chlorine conductance gated by gamma-aminobutyric acid (GABA) and L-glutamate in the medial pleural neurons of aplysia was studied using voltage clamp technique and a continuous microperfusion system that allowed rapid agonist application. Both GABA and glutamate elicited current responses that rapidly activated and then decayed. Glutamate response could be blocked by perfusion of aspartate or taurine and the GABA current showed voltage dependence. Thus the currents exhibited cross desensitization. It has been found that very low concentrations of acetylcholine (10(-8) to 10(-14) M) which have no electrophysiologic responses of their own, modulate the response to a constant application of GABA. During cooling the preparation blocked this effect, it is possible to suggest that the small doses of acetylcholine effect the membrane chemosensitivity through the cell biochemical mechanism.