Vasoactive intestinal polypeptide does not affect thyroid follicular cell membrane potential or input resistance.

It has been suggested that vasoactive intestinal polypeptide (VIP) has a role as a neurotransmitter and that it participates in the control of hormone release from thyroid follicles. Many hormones and neurotransmitters alter the ionic permeability properties of the plasma membrane of their target cells when they bind to their receptors. Concentrations of VIP able to elicit complex time-dependent changes in rat thyroidal cyclic nucleotide levels did not affect follicular cell membrane potential or input resistance. The suggestion is made that the findings may indicate that Ca2+ is not involved in the initial stages of stimulus-secretion coupling following VIP binding to its receptor on the follicular cell.