Abstract
Properties of electrical responses evoked by cholinergic nerve stimulation were investigated in single bundle preparation of circular smooth muscle isolated from the guinea-pig gastric antrum. In the absence of nitrergic components by inhibiting the biosynthesis of nitric oxide with nitroarginine, smooth muscle produced periodical generation of slow potentials. Transmural nerve stimulation (TNS) evoked an apamin-sensitive inhibitory junction potential (IJP) and following atropine-sensitive depolarization response, the latter was either a transient depolarization with enhanced generation of unitary potentials or a slow potential, when TNS was applied at the interval between slow potentials. TNS elicited a generation of slow potentials only when it was applied at a certain period of time after the cessation of slow potentials, i.e., there was a high-threshold period for the generation of slow potentials by TNS. The high-threshold period was about 10s after cessation of slow potentials, and it was increased to about 20s in the presence of chelerythrine and decreased to about 6s by phorbol esters. It is concluded that neuronal cholinergic excitation of gastric muscle involves an activation of PKC, and the high-threshold period for the generation of slow potentials by TNS may be causally related with the low activity of PKC. [Jpn J Physiol 54 Suppl:S123 (2004)]
