POSTSYNAPTIC EFFECT OF I.V. ANAESTHETIC AGENTS AT THE NEUROMUSCULAR JUNCTION

Abstract

The effects of sodium thiopentone 19–757μmol/litre, sodium pentobarbitone 25–806 μmol/litre, propanidid 74–1186 μol/litre, Althesin 55–220 μol/litre, diazepam 17.6–140 μmol/litre and ketamine 1.8–116.8 μmol/litre on the time–course of miniature end–plate currents of the excised mouse diaphragm were investigated. The currents were detected by means of extracellular electrodes and recorded with a transient recorder. The drugs had no significant effect on the growth phase of the current, but all six shortened the time-constant of the decay phase. This reduction in the duration of end-plate currents reduced the amplitude of postsynaptic potentials. A similar effect at central synapses may account for a failure of synaptic transmission caused by anaesthetic drugs and it is suggested that a reduction in the lifetime of open postsynaptic ionic channels is a common action of anaesthetic drugs.