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 polypeptide on calcium currents (ICa) in acutely dissociated neurons from the adult rat superior cervical ganglion. We found that NPY inhibited the ICa with an estimated IC50 value of 140 nM. This inhibitory effect appeared to be restricted to a subset of cells which were smaller in diameter than the general population. The effect of NPY on the ICa was prevented by pretreatment with pertussis toxin, suggesting the involvement of a GTP-binding protein of the Gi or Go subtype. omega-conotoxin GVIA also occluded the effects of NPY, which suggests that these were directed toward N-type Ca++ channels. The effects of NPY were mimicked by the fragment NPY (13-36) but not by peptide YY, indicating that a receptor distinct from a Y1- or a Y2-like NPY receptor was involved. Finally, we also observed that pancreatic polypeptide inhibited the ICa, suggesting that a pancreatic polypeptide receptor is also present on superior cervical ganglion neurons.