Voltage-dependent actions of short-chain polymethylene bis-trimethylammonium compounds on sympathetic ganglion neurons

Abstract

Effects of polymethylene bis-trimethylammonium compounds (with 4-7 carbons in the polymethylene chain, C4-C7) on voltage-dependence of fast excitatory postsynaptic current (EPSC) were studied in voltage-clamped neurons of the isolated rabbit superior cervical ganglion. All these compounds shortened the EPSC decay (which remained single-exponential) and decreased (or reversed) the dependence of the EPSC decay on membrane hyperpolarization. All drugs slightly decreased the EPSC amplitude; in addition, C6 and C7 decreased their dependence on membrane hyperpolarization. It is suggested that shortening of the EPSC decay produced by ganglion-blocking agents results from their binding to the open ionic channel (channel-blocking effect). The ratio of channel-blocking activities of these drugs correlates with the well-known ratio of their ganglion-blocking activities. It is suggested that the channel-blocking activities of polymethylene bis-trimethylammonium compounds determine their ganglion-blocking activities. The model of channel-blocking action is discussed.