Effect of volatile anaesthetics on the electrical activity and the coupling coefficient of weakly electrically coupled neurones.

1. The application of the volatile anaesthetics, halothane and isoflurane (1% v/v and 2% v/v), to the CNS of Lymnaea reduced the firing frequency of the small weakly coupled pedal A cluster (PeA) neurones, which eventually become quiescent. There was no change in their resting membrane potential. 2. Met-enkephalin significantly increased the coupling coefficient between PeA neurones. 3. The volatile anaesthetics decreased the coupling coefficient even in the presence of met-enkephalin. 4. These effects were dose dependent and the effects of halothane were more rapid than those of isoflurane, reflecting their different anaesthetic potencies.