NEUROPEPTIDE-Y AND PANCREATIC-POLYPEPTIDE REDUCE CALCIUM CURRENTS IN ACUTELY DISSOCIATED NEURONS FROM ADULT-RAT SUPERIOR CERVICAL-GANGLIA

We examined the effects of neuropeptide Y (NPY) and pancreatic polypep tide on calcium currents (1Ca) in acutely dissociated neurons from the adult rat superior cervical ganglion. We found that NPY inhibited the I(Ca) with an estimated IC50 value of 140 nM. This inhibitory effect appeared to be restricted to a subset of cells which were smaller in d iameter than the general population. The effect of NPY on the I(Ca) wa s prevented by pretreatment with pertussis toxin, suggesting the invol vement of a GTP-binding protein of the G(i) or G(o) subtype. Omega-con otoxin GVIA underbar also occluded the effects of NPY, which suggests that these were directed toward N-type Ca++ channels. The effects of N PY were mimicked by the fragment NPY (13-36) but not by peptide YY, in dicating that a receptor distinct from a Y1- or a Y2-like NPY receptor was involved. Finally, we also observed that pancreatic polypeptide i nhibited the I(Ca), suggesting that a pancreatic polypeptide receptor is also present on superior cervical ganglion neurons.