Calcitonin Gene-Related Peptide Relaxes Cholecystokinin-Induced Tension in Iguana iguana Gallbladder Strips

The presence of a calcitonin gene-related peptide (CGRP)-like material was demonstrated in the iguana, Iguana iguana, gallbladder using immunocytochemistry. An intense reaction was observed in nerves located in the smooth muscle layers and associated blood vessels but no immunoreactive cell bodies were found. In vitro tension studies using gallbladder strips showed that chicken CGRP was more potent in relaxing cholecystokinin-induced tension than either human or rat CGRP. The use of glibenclamide and l -NG-nitro-arginine methyl ester suggested that this relaxation is mediated by either nitric oxide release from nerves stimulated by CGRP or by CGRP acting directly on the gallbladder smooth muscle.