Differences between muscular receptors and neural receptors for cholecystokinin-octapeptide in the guinea-pig gallbladder.

To investigate the differences between muscular and neural receptors for cholecystokinin-octapeptide (CCK-OP) in the guinea-pig gallbladder, we studied the effects of dibutyryl cyclic GMP (dbc GMP) on CCK-OP-evoked contraction and [3H]acetylcholine (ACh) release. 10(-3) M dbc GMP significantly reduced CCK-OP (10(-8) M)-evoked contractions without affecting the peptide-induced [3H]ACh release. It is suggested that there are two types of CCK-OP receptors in the guinea-pig gallbladder (dbc GMP-sensitive muscular receptors and dbc GMP-insensitive neural receptors).