Involvement of calcium channels in short-term desensitization of muscarinic receptor-mediated cyclic GMP formation in mouse neuroblastoma cells.

Incubation of mouse neuroblastoma cells (clone N1E-115) with Mn2+ resulted in a rapid and transient increase in cyclic GMP formation. This effect appears to be due to an increase in calcium influx because it did not occur in the absence of extracellular calcium or in the presence of verapamil, a calcium transport inhibitor. In addition, Mn2+ inhibited muscarinic receptor-mediated cyclic GMP responses. The ability of Mn2+ to increase cyclic GMP levels was markedly diminished in cells desensitized to the effects of carbamoylcholine, suggesting that this densensitization involves inactivation of calcium entry.