SUBTYPES OF VOLTAGE-SENSITIVE CALCIUM CHANNELS IN CULTURED RAT-BRAIN NEURONS

Subtypes of voltage-sensitive calcium channels have been investigated in cultured rat brain neurons using two classes of specific probes, dihydropyridine compounds and ω-conotoxin. Membranes prepared from cultured neurons contain specific binding sites for [3H]PN200-110, a dihydropyridine antagonist, and for 125I-ω-conotoxin with a stoichiometry of about 1:1. A depolarization induced 45Ca2+ influx into intact brain neurons was partially inhibited by a dihydropyridine antagonist, nifedipine and stimulated by a dihydropyridine agonist, Bay K8644. This dihydropyridine sensitive 45Ca2+ flux was insensitive to ω-conotoxin at concentrations which saturate the specific toxin binding sites indicating that in cultured brain neurons, dihydropyridine-sensitive calcium channels are not sensitive to ω-conotoxin. © 1990.