Vasoactive intestinal peptide suppresses migrating myoelectric complex of rat small intestine independent of nitric oxide

The involvement of nitric oxide (NO) in the biological response to vasoacti ve intestinal peptide (VIP) on the migrating myoelectric complex (MMC) of s mall bowel and systemic arterial blood pressure was investigated in the rat . Animals were supplied with bipolar electrodes for electromyography of the small intestine and blood pressure was assessed by a pressure transducer c onnected to a carotid artery. In the first session, N-omega-nitro-L-arginin e (L-NNA) was administered intravenously at 1, 2, 4 and 20 mg kg(-1). Effec ts of L-NNA at 1 and 20 mg kg(-1) were also studied after L-arginine 300 mg kg(-1). In the second session, intravenous infusion of VIP 500 pmol kg(-1) min(-1) was administered before and after L-NNA at 1 and 20 mg kg(-1). L-N NA at increasing doses stimulated myoelectric spiking of the small bowel un til at 4 mg kg(-1) the MMC was disrupted and irregular spiking induced. Nei ther at 1 nor 20 mg kg(-1) did L-NNA affect the inhibitory motility respons e or decrease of blood pressure induced by VIP at a dose of 500 pmol kg(-1) min(-1). Our results show that effects of VIP on motility of the small int estine and systemic arterial blood pressure are direct and not dependent on NO as a common final link.