On the purinergic system in rat duodenum : existence of P1and P2receptors on the smooth muscle

Abstract
In rat duodenum, in vitro, in the presence of atropine and guanethidine, ATP administration caused a tetrodoxin-insensitive relaxation followed by a rebound contraction. A similar response was obtained also after electrical field stimulation (EFS) of non-adrenergic, non-cholinergic (NANC) nerves, α, β-methyleneATP and theophylline antagonized the response to ATP, but they failed to affect the noradrenaline- and EFS-induced relaxation. These results suggest that P1 and P2 receptors are present in rat duodenum, but their activation is not responsible for the inhibitor effects due to the NANC nerves.