Fig. 6. Single vasoconstrictor muscle fiber is innervated by several excitatory axons. (A) Relationships between stimulus intensities and EJPs. The pericardial nerve was stimulated by a 1 ms pulse of various intensities as indicated. Four records are superimposed. Fast vertical deflections are stimulus artifacts. Note that the increase in stimulus intensity not only changes the peak amplitude of EJP, but also the shape of EJP. (B) Effect of 10^–3 mol l^–1 hexamethonium on EJPs evoked by the stimulus train (1 ms, 1.6 V, 10 Hz) for 0.5 s.