Vagal release of IR-VIP and IR-gastrin from the isolated perfused rat stomach.

The effects of electrical stimulation of the vagus at varying pulse widths on the release of immunoreactive VIP (IR-VIP) and IR-gastrin have been investigated, using the isolated perfused rat stomach preparation. Electrical stimulation of vagal trunks at a pulse width of 0.1 msec duration yielded no change in basal IR-VIP levels whereas a pulse width of 5.0 msec produced a prompt sustained increase. Stimulation at either pulse width evoked gastrin release. Atropine blocked the vagal release of IR-gastrin but not IR-VIP whereas hexamethonium blocked both responses. Exogenously administered porcine VIP, at concentrations mimicking endogenously released levels, was used in an attempt to reproduce the effects observed by vagal stimulation. Exogenous VIP had no effect on gastrin or somatostatin-like immunoreactivity (SLI) release. These in vitro studies support a role for VIP as a neurotransmitter released from the stomach by low-threshold non-cholinergic vagal fibres, but involving autonomic ganglia.