VIP inhibits high voltage-gated calcium channel currents of hamster submandibular ganglion neurons.

In this study, we investigated the modulation of calcium channels by vasoactive intestinal polypeptide (VIP) in hamster submandibular ganglion (SMG) cells using the whole-cell patch clamp technique. VIP (1 microM) inhibited the high voltage-gated calcium channels in the SMG neurons via activation of VIP receptors and G-protein coupled to these receptors, but did not affect the low voltage-gated calcium channels. VIP at 1 microM reduced the peak amplitude of the maximum high voltage-gated calcium current by 26.0 +/- 6.2% (mean +/- S.E., n = 5) and slowed the rising phase of the calcium current. The time to peak of the maximum high voltage-gated calcium current was prolonged from 16.8 msec to 22.4 msec. In a representative cell, 1 microM VIP reduced the peak amplitude of maximum high voltage-gated calcium current by 50.5% and the amplitude at the end of voltage step after 300 msec by 51.9%. The VIP-induced inhibition of the calcium current was produced in a voltage-dependent manner. Inhibition was maximal (50.5%) at the level of -20 mV. Therefore, VIP inhibits both transient and sustained types of high voltage-gated calcium channels in the hamster SMG neuron.