Effects of procaine and lignocaine on electrical and mechanical activity of smooth muscle of sheep carotid arteries.

1 Procaine in concentrations up to 20 mM facilitated or induced electrical and mechanical activity in arterial smooth muscle, even with tetrodotoxin present.2 Procaine (up to 20 mM) caused relaxation when electrical activity was blocked by prior potassium depolarization.3 Procaine (1 mM) reduced mechanical responses to noradrenaline (1 muM) which were not accompanied by action potentials. It generally reduced mechanical responses to noradrenaline (1 mM) while increasing electrical activity induced by this.4 Lignocaine (1 mM) did not facilitate electrical activity significantly; it relaxed arteries in saline or potassium-rich solution and reduced mechanical responses to noradrenaline.5 High concentrations of procaine (at least 80 mM) or lignocaine (at least 20 mM) blocked electrical activity and caused contraction followed by relaxation and complete unresponsiveness.