Vasoactive intestinal polypeptide alters GH3/B6 pituitary cell excitability.

The effects of the prolactin secretagogue vasoactive intestinal peptide (VIP) on the membrane excitability of clonal prolactin-secreting (GH3/B6) cells were studied using the whole-cell configuration of the patch recording technique. Submicromolar concentrations of VIP affected membrane excitability in more than half the cells tested, increasing the frequency of spontaneous Ca2+-dependent action potentials and prolonging individual action potentials, as well as changing their rheobase. Under voltage clamp, VIP induced changes in several voltage-sensitive conductances at both instantaneous and steady-state times. Some of these changes in membrane excitability may be related to VIP's stimulatory effects on prolactin secretion.