Influence of [4Cl-D-Phe6,Leu17]VIP on VIP- and central TRH-induced gastric hyperemia.

The specific VIP receptor antagonist, [4Cl-D-Phe6,Leu17]VIP, infused i.v. blocked close-intra-arterial infusion of VIP-induced increase in gastric mucosal blood flow (GMBF, measured by the hydrogen gas clearance), and decrease in mean arterial blood pressure while not influencing basal levels in urethane-anesthetized rats. The thyrotropin-releasing hormone (TRH) stable analog, RX 77368, injected intracisternally (IC, 30 ng) increased GMBF and blood pressure. The VIP antagonist did not significantly reduce the GMBF response to IC RX 77368 while enhancing the rise in blood pressure. These findings indicate that [4Cl-D-Phe6,Leu17]VIP is an antagonist for exogenous VIP-induced gastric hyperemia and hypotension and that VIP modulates the systemic blood pressure response to IC RX 77368 at 30 ng while not playing a primary role in the increase of GMBF.