Résumé
Dopamine induces a decrease in voltage-dependent Ca2+ current in identified neurons of the snail H. aspersa. This effect is blocked by intracellular injection of activated B. pertussis toxin and of an affinity-purified antibody against the alpha subunit of bovine G(0). protein. The dopamine effect is mimicked by intracellular injection of mammalian alpha(0). In snail nervous tissue, pertussis toxin ADP-ribosylates a single protein band on SDS gels, and this band is recognized in immunoblots by the anti-alpha(0) antibody. We propose that this is a 40 kd subunit of a molluscan G protein immunologically related to alpha(0) and that it mediates the effect of dopamine on Ca2+ currents in identified snail neurons.