AbstractEffects of neurokinin A, neurokinin B, substance P and neuropeptide K on myoelectric activity in the small intestine were related to intestinal transit of a radioactive marker in fasted conscious rats. Myoelectric activity was recorded using bipolar electrodes implanted at 5, 20 and 35 cm distal to pylorus. Intravenous infusions of neurokinin A, neurokinin B and neuropeptide K at doses of 50–200 pmol kg−1min−1and substance P at doses of 100–300pmol kg−1min−1, disrupted migrating myoelectric complexes and induced irregular spiking. These effects were not prevented by atropine, hexamethonium or mepyramine. However, the effect of neurokinin A was attenuated by spantide. The irregular spiking induced by the tachykinins was associated with increased transit of the marker in animals receiving neurokinin A and neurokinin B, but not substance P and neuropeptide K. We conclude that the tachykinins activate the smooth muscle layers of the small intestine in the rat by mechanisms involving neurokinin receptors, but not muscarinic, nicotinic or H1‐receptors. Our results suggest a role for tachykinins in regulation of motility by induction of irregular spiking, which may stimulate transit through the sm