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Module 7: Figure neural evoked contractions

Electrical and mechanical responses to neural stimulation of guinea-pig bladder.

Strips of smooth muscle cells were given a train of stimuli at 20 Hz for 1 s (black bar), which would have released both ATP and acetylcholine (ACh). A. The spontaneous single action potentials (trace a) preceding the stimulation failed to induce a contraction (trace b). During the stimulation period there was a rapid acceleration of action potentials and a large contraction. Following the stimulation the increased rate of action potentials continued for a while. B. The same procedure was repeated in the presence of α,β-methylene ATP, which inhibits ATP to reveal the action of ACh. There were no action potentials during the 1 s stimulus period, but thereafter the membrane depolarized and there was a marked increase in the frequency of action potentials associated with an oscillatory period of contractions. Reproduced from Hashitani et al (2000).