Activators of G-proteins increase the plasticity of cholinoreceptors of common snail neurons.

The influences of depth of damping of the inward current evoked by acetylcholine (the ACh-current), of two nonhydrolyzable analogs of GTP, which irreversibly activate G-proteins, namely 5'-guanylylimidodiphosphate (Gpp(NH)p) and guanosine 5'-O-(3-thiotriphosphate) (GTP-g-S), were investigated in identified RPa3 and LPa3 neurons of the common snail using the two-electrode voltage clamp technique. An irreversible deepening of the damping of the ACh-current following intracellular iontophoretic injections (-2 nA, 10 min) of Gpp(NH)p and GTP-g-S was demonstrated. A conclusion was reached regarding the participation of G-proteins in the molecular mechanism of the positive regulation of plasticity of cholinoreceptor neurons. Both of the G-protein activators used demonstrated a new atypical influence on the damping of the ACh-current, a disruption of its monotonic character. The hypothesis is advanced that the cause of such an influence lies in the oscillations of the concentration of intracellular Ca2+ induced by G-protein activators.