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 (I(Ca)) 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 diameter than the general population. The effect of NPY on the I(Ca) was prevented by pretreatment with pertussis toxin, suggesting the involvement of a GTP- binding protein of the G(i) or G(o) subtype. ω-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 I(Ca), suggesting that a pancreatic polypeptide receptor is also present on superior cervical ganglion neurons.