Fig. 2. ENpa and GSPRFFamide depress the contraction of the vasoconstrictor muscle evoked by the stimulation of the pericardial nerve. (A) Effects of 10^–7 mol l^–1 ENpa (Ai) and 10^–7 mol l^–1 GSPRFFamide (Aii) on the contraction evoked by a train of the electrical pulse (1 ms, 1.6 V, 10 Hz) for 1 s. The stimulus train was applied every 20 s. Peptides were applied for 2 min as indicated by bars. Ai and Aii are from the same preparation. (B) Concentration–response relationships of the effects of ENpa and GSPRFFamide. Amplitude of the most depressed contraction after the peptide application is normalized to that of the control contraction and the mean ± S.E. was plotted against the concentration of the peptides (N=36). (C) Time-dependent effects of the peptide actions. Amplitude of the muscle contraction was normalized to the control contraction just before the peptide application and plotted against the time (N=3). 10^–5 mol l^–1 of ENpa or GSPRFFamide was applied for 2 min as indicated.