Tachykinins play a minor role in mediating the third phase of the contractile response to vagal nerve stimulation of the guinea-pig oesophagus

The aim of this study was to determine whether tachykinin receptors might b e involved in the mediation of the atropine- and capsaicin-sensitive third phase of a triphasic contractile response to vagal nerve stimulation of the guinea-pig isolated oesophagus. The third phase was inhibited 23.3 +/- 1.7 % (P < 0.001, n = 5) and 30.8 +/- 9.0% (P < 0.05, n = 5) by the NK3 recepto r antagonist, SR 142 801 (0.1 and 1 mu M respectively). SR 142 801 (0.1 and 1 mu M) had no significant effect on the response to a submaximal concentr ation of acetylcholine (0.1 mM, n = 4). The third phase was not significant ly affected by NK1 or NK2 receptor antagonists. Thus, in the guinea-pig oes ophagus, it appears that while NK1 and NK2 receptors are not involved, NK3 receptors play a minor role in mediating a contractile response when affere nt neurones are excited by vagal nerve stimulation. (C) 2000 Harcourt Publi shers Ltd.