Acute and neonatal capsaicin treatment inhibit jejunal amino acid absorption through a sodium-dependent mechanism. Barada, K. A., S. S. Dika, S. F. Atweh, N. E. Saad[acute]e, and C. F. Nassar. DEPARTMENTS OF MEDICINE, PHYSIOLOGY AND HUMAN MORPHOLOGY, AMERICAN UNIVERSITY OF BEIRUT, LEBANON
APStracts 3:0246G, 1996.
It was recently shown that capsaicin inhibits alanine absorption in the rat jejunum via mechanisms that involve intestinal capsaicin -sensitive primary afferents (CSPA). This study provides further evidence that the effect of capsaicin is neurally mediated and demonstrates that CSPA fibers regulate sodium dependent amino acid absorption. In vivo, basal alanine absorption in rats neonatally treated with capsaicin was reduced by 35% below control. Furthermore, intraluminal perfusion of 400 [mu]M capsaicin reduced jejunal alanine absorption by 31% in sham rats but had no significant effect in rats neonatally treated with capsaicin. In vitro, capsaicin reduced significantly the uptake of alanine and proline by jejunal strips, but had no effect on the uptake of lysine. Tetrodotoxin (0.2[mu]M) partially blocked the effects of capsaicin, but didn't itself affect alanine absorption. Capsaicin reduced unidirectional mucosal to serosal alanine (1mM) influx by 33%, an effect which becomes significant after 5 min of preincubation with capsaicin. Neonatal capsaicin treatment reduced basal alanine influx in jejunal strips by 37%, however, preincubation of these strips with capsaicin had no significant effect. Kinetic analysis of alanine steady-state uptake and influx by jejunal strips incubated with capsaicin revealed that capsaicin reduced the sodium dependent component of alanine influx into intestinal epithelial cells. Long term sensory denervation by capsaicin decreased also the sodium dependent component of alanine absorption. These data suggest that intestinal capsaicin primary afferents regulate sodium dependent amino acid absorption. 

Received 18 January 1996; accepted in final form 25 October 1996.
APS Manuscript Number G27-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996