Direct coupling of a G-protein to dihydropyridine binding sites

Electrophysiological data support the existence of GTP-binding proteins interacting with voltage dependent calcium channels. Along this line the present study investigates the effect of GMP-PNP, a stable GTP analogue, on the displacement of [3H]-PN 200-110 binding by agonist and antagonist dihydropyridines in synaptic membranes prepared from rat cortex. The results show that GMP-PNP increases the ability of the agonist dihydropyridine BAY K 8644 to displace [3H]-PN 200-110 binding. The in vivo treatment with Pertussis Toxin abolishes the effect produced by the non-hydrolysable GTP analogue.