Fig. 6. Modulation of neurally evoked contractions by 5-HT is temperature dependent. (A) Neurally evoked contractions recorded under control conditions (lower traces) and in the presence of 50 nmol l^–1 5-HT (upper traces) at the indicated temperatures. Each trace is the average of ten consecutive recordings. (B) Temperature dependence of neurally evoked contraction strength in muscle fibers (N=6) in the absence (open symbols) and presence (closed symbols) of 5-HT (50 nmol l^–1). Control data are normalized relative to the average contraction amplitude recorded at 2°C (error bars are not larger than the symbols); 5-HT data are normalized relative to the potentiating effect of 5-HT on contraction amplitude (an increase of 1112%) at 2°C in the same preparations. (C) Potentiation of neurally evoked contractions by 50 nmol l^–1 5-HT recorded at bath temperatures between 2°C and 22°C (N=5 muscle fibers at 20°C and 22°C, N=6 at all other temperatures). Symbols illustrate the logarithm of the ratio of neurally evoked contraction strength after application of 5-HT with respect to the control value at the same temperature. Asterisks indicate values that are significantly different from data recorded at 2°C (independent t-test, P<0.05).