CHOLECYSTOKININ AND NEUROPEPTIDE-Y RECEPTORS ON SINGLE-RABBIT VAGAL AFFERENT GANGLION NEURONS - SITE OF PREJUNCTIONAL MODULATION OF VISCERAL SENSORY NEURONS

A [I-125]cholecystokinin (CCK) analog and [I-125]peptide YY (PW) were used to localize and characterize CCK and neuropeptide Y (NPY) recepto r binding sites in the rabbit vagal afferent (nodose) ganglion. High c oncentrations of CCK and NPY binding sites were observed in 10.6% and 9.2% of the nodose ganglion neurons, respectively. Pharmacological exp eriments using CCK or NPY analogs suggest that both subtypes of CCK (C CK-A and CCK-B) and NPY (Y1 and Y2) receptor binding sites are express ed by discrete populations of neurons in the nodose ganglion. These re sults suggest sites at which CCK or NPY, released in either the nucleu s of the solitary tract or a peripheral tissue, may modulate the relea se of neurotransmitters from a select population of visceral primary a fferent neurons. Possible functions mediated by these receptors includ e modulation of satiety, opiate analgesia, and the development of morp hine tolerance.