Considering the roles of the α 2-adrenoceptor and nitric oxide (NO) system in gastrointestinal tract, we studied the possible interaction of α 2-adrenoceptor agonist clonidine that used in anesthesia and intensive care because of its sedative, analgesic and anesthetic properties, with the NO system in rat ileum relaxation.

The influence of the NO on the inhibitory effect of α 2-adrenoceptor agonist clonidine on the contractile responses given to the electrical field stimulation was investigated in rat ileum strips. In different series, the effect of clonidine (10-8-10-5M) in cumulative concentrations were studied in the presence of NO precursore L-arginine (L-Arg) (10-4м), NO synthase inhibitor L-nitro-argininemethyl ester 2-adrenoceptor antagonist yohimbine (10-6м) and their α (L-NAME) (10-4м) and various combinations on isolated rat ileum in vitro.

The relaxation responses elicited by the increasing concentrations of clonidine abolished in the presence of yohimbine. In the presence of L-Arg, relaxation responses were potentialised, but in a different serie the presence of L-NAME didn't change the relaxation effects. The inhibitory effect of clonidine increased in the presence of L-Arg shows that clonidine and nitric oxide probably interacts on electrically stimulated relaxation responses in rat ileum.