Abstract
ATP is now known as a substance that is released from injured/stimulated cells to induce or augment pain. In the urinary bladder ATP is released from the endothelium when the bladder is stretched, and thus released ATP stimulates sensory nerve terminals to transmit the stretched state of the bladder to the central nervous system. We hypothesize that the same happens in the skeletal muscle, and measured ATP release upon mechanical stimulation (compression) of the muscle. The extensor digitorum longus muscle was excised from the deeply anesthetized rats, and superfused with Krebs-Henseleit solution. The superfusate was sampled at a rate of 0.8 ml/min and its ATP concentration was measured with Luciferin-Luciferase method. At first we examined ATP release to repetitive application of 20 g force/10 s stimulation, which was used for the study of nociceptor characteristics, with a servo-controlled mechanical stimulator with intervals of 30 min. ATP release was clearly decreased on repetition of the mechanical stimulus. Then we examined stimulus response relationship. The muscle was stimulated five times at 5, 10, 20 and 40 g forces at a rate of 10 g/s. ATP release was increased roughly stimulus-strength dependently in this range. Whether ATP thus released transmits mechanical event to nociceptors is to be studied. [J Physiol Sci. 2006;56 Suppl:S179]
