Fig. 4. Dose-dependent inhibitory effect of atropine and tubocurarine on 1 mmol l^–1 ACh-induced luminescence from arm segment of A. filiformis. Values are means + S.E.M. of maximal intensities of light emitted, expressed as a percentage of those measured in control arm segments, not treated with cholinergic antagonists. Asterisks indicate significant differences between control and treated arm segments (*P<0.05, **P<0.01).