Fig. 4. The enterin inhibits the phasic contraction of the anterior aorta evoked by electrical stimulation of the vulvar nerve. (A) Effect of 10^-8 moll^-1 ENpa on the phasic contraction. To evoke a phasic contraction of the aorta, the vulvar nerve was stimulated by repetitive pulses (5V, 1 ms, 10 Hz) for 1 s. (B) The concentration—response of ENpa. The amplitude of the evoked contraction in the presence of ENpa was normalized to the one obtained before the application of the peptide. Values are means ± S.E.M. (N=4) plotted against the concentration of the peptide. The smooth line is a best-fit of the equation described in Materials and methods. r₁, r₂ and n were fixed to 0, 100 and -1, respectively. logx0 was estimated to be -8.1.