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Am J Physiol Gastrointest Liver Physiol 285: G325-G331, 2003. First published March 26, 2003; doi:10.1152/ajpgi.00411.2002
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NEUROREGULATION AND MOTILITY

Peristalsis regulation by tachykinin NK1 receptors in the rabbit isolated distal colon

Luciano Onori,1 Annalisa Aggio,1 Gennaro Taddei,1 Maria F. Loreto,1 Rachele Ciccocioppo,1 Riccardo Vicini,2 and Marcello Tonini2

1Department of Internal Medicine and Public Health, University of L'Aquila, 67100 L'Aquila; and 2Department of Physiological and Pharmacological Sciences, University of Pavia, 27100 Pavia, Italy

Submitted 24 September 2002 ; accepted in final form 18 March 2003

In the gastrointestinal tract, tachykinin NK1 receptors are widely distributed in a number of neuronal and nonneuronal cells involved in the control of gut motor activity. In particular, in the rabbit isolated distal colon, which is a suitable model system to investigate the contribution of tachykinins as noncholinergic excitatory transmitters, the influence of NK1 receptors in the regulation of peristalsis is not known. The selective NK1-receptor antagonists SR-140333 (0.3 and 1 nM) and MEN-10930 (0.3–10 nM) significantly enhanced the velocity of rabbit colonic propulsion to submaximal stimulation. The prokinetic effect of SR-140333 was prevented by N{omega}-nitro-L-arginine (L-NNA), a nitric oxide synthase inhibitor, indicating that NK1 receptors located on nitrergic innervation exert a functional inhibitory restraint on the circular muscle and probably on descending excitatory and inhibitory pathways during propulsion. Conversely, the selective NK1-receptor agonist septide (3–10 nM) significantly inhibited colonic propulsion. In the presence of L-NNA, the inhibitory effect of septide was reverted into a prokinetic effect, which is probably mediated by the activation of postjunctional excitatory NK1 receptors.

myenteric neurons; excitatory pathways; inhibitory pathways


Address for reprint requests and other correspondence: L. Onori, Dept. of Internal Medicine and Public Health, Univ. of L'Aquila, Via S. Sisto 22/E, 67100-L'Aquila, Italy (E-mail: annaggio{at}katamail.com).






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