Studies on the mode of action of bretylium and guanethidine in post-ganglionic sympathetic nerve fibres

Abstract

1. The effects of bretylium and guanethidine on the nerve terminal impulse and transmitter release from sympathetic postganglionic nerve terminals in the guinea-pig vas deferens have been studied in vitro using focal extracellular recording. Excitatory junction currents (EJCs) were used as a measure of transmitter release. 2. Both bretylium and guanethidine altered the configuration of the nerve terminal impulse in a manner consistent with their being local anaesthetics. 3. Bretylium (1–3 μM) only completely inhibited transmitter release when impulse propagation in the sympathetic nerve terminal was blocked. 4. In contrast, guanethidine (1–10 μM) could block transmitter release with little e..