1998/11/01 by Anthony Krantis, Kamal Mattar, Ian Glasgow
paper · doi:10.1152/ajpgi.1998.275.5.g897
Spontaneous relaxations occurring within motor activity in the rat gastroduodenum in vivo can be distinguished by their dependence on either nitric oxide (NO) or ATP. We examined the interaction of γ-aminobutyric acid (GABA) and vasoactive intestinal peptide (VIP) within pathways controlling this activity in the antrum (S) and duodenum (D) of anesthetized Sprague-Dawley rats, using miniaturized extraluminal foil strain gauges oriented perpendicular to (S 1 , D 1 ) or in the axis of (S 2 ) the circular smooth muscle. The NO synthase inhibitor N G -nitro-l-arginine methyl ester (l-NAME; 10 mg/kg iv) attenuated ( P A receptor antagonist bicuculline (350 μg/kg sc) had similar effects. The GABA A agonist 3-amino-1-propanesulfonic acid stimulatedl-NAME-sensitive relaxations at S 1 and D 1 . Propagating “grouped” responses were unchanged. VIP (6 μg/kg iv) always induced a relaxation of the duodenum, which was attenuated by bicuculline andl-NAME. VIP caused simultaneous responses at S 1 and S 2 ; however, the antrum displayed either contraction or relaxation in response to VIP. All antral relaxations in response to VIP were attenuated ( P 1 were sensitive to bicuculline. VIP-induced contractions were also unaffected. GABA A receptors mediate the pathway(s) controlling NO-related spontaneous relaxations of the antrum and duodenal circular muscle. All VIP-induced relaxations are mediated by NO. Spontaneous relaxations of the rat gastroduodenum include responses that involve a GABA A ergic NO-related pathway, which is targeted by VIP. In addition, VIP can target NO relaxations of the antrum via other pathways.