Effects of intraventricular administration of vasoactive intestinal peptide and neurotensin on salivary secretion and blood pressure in the rat

Studies were carried out to investigate central actions of vasoactive intestinal polypeptide (VIP) and neurotensin (NT) on systemic blood pressure (BP), heart rate (HR) and salivary secretion in urethane-anesthetized male rats. Intraventricular (i.c.v.) administration of VIP caused dose-related increases in BP, HR and salivary secretion. Nearly maximum values were obtained at the dose of 2.0 micrograms for BP and 10.0 micrograms for salivary secretion, whereas the increase in HR did not attain the maximum even with the dose of 10.0 micrograms. Administration of hexamethonium (i.v.) completely blocked the increasing response of BP and HR, and the administration of pimozide (i.p.) or phenoxybenzamine (i.v.) reduced them. The increasing response of salivary secretion was almost completely blocked by all of the drugs. The administration of NT (i.c.v.) produced no change in the BP, HR and salivary secretion. The present results indicate that, 1) centrally administered VIP may somehow augment the sympathetic nerve discharge and/or adrenal medulla secretion, and 2) central VIP may play a role in the control of salivary regulation, probably through sympathetic nerves.