We have further characterized a putative receptor-operated Ca2+ channel that is activated by histamine and guanosine 5′-[beta gamma-imido]triphosphate. Insensitivity to verapamil, diltiazem or nicardipine, but inhibition by Ni2+ and SK&F 96365, further identify the channel with receptor-mediated Ca2+ entry in intact cells. Inhibition of the channel by cyclic-GMP-dependent protein kinase may contribute to vascular relaxation in response to nitrovasodilators.
