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 desensitization involves inactivation of calcium entry.