Fig.2. Effect of proctolin on caffeine-induced contractures. (A) Potentiation of caffeine (10mmoll^-1) contracture by 1µmoll^-1 proctolin. Two controls are shown, before and after the exposure to proctolin. (Caff, caffeine; Proc, proctolin). (B) Averages of normalised tensions obtained from 4 experiments. Control represents the average of three caffeine contractures per experiment prior to the proctolin tests. Values are means ± S.D., *P<0.05, Student’s t-test.