ACTIONS OF CALCITONIN-GENE-RELATED PEPTIDE IN GUINEA-PIG GALLBLADDER GANGLIA

The actions of calcitonin gene-related peptide (CGRP) have been determ ined from intracellular recordings obtained from gallbladder neurons i n intact whole mount preparations. In most cells, pressure microejecti on of CGRP elicited a slow monophasic depolarization, 4 mV in amplitud e, that was associated with a decrease in input resistance and increas ed excitability. The CGRP-induced depolarization was attenuated in a l ow-Na+ solution and had a reversal potential of -8 mV. In 10% of the c ells, microejection of CGRP elicited a biphasic response that was comp osed of a rapid transient depolarization followed by a slow depolariza tion that was similar to the monophasic response. Addition of CGRP (1- 10 nM) to the bathing solution elicited a monophasic depolarization an d desensitized the cells to applications of CGRP by microejection. For skolin, applied either by microejection or bath application, also depo larized gallbladder neurons and produced cross-desensitization to CGRP . Responses to substance P were not enhanced by CGRP, and CGRP did not affect fast synaptic responses. It is concluded that CGRP may contrib ute to a local axon reflex response in gallbladder ganglia.