Differential actions of volatile anaesthetic agents on a single isolated neurone

The precise mechanism(s) and site(s) of action of general anaesthetic agents remain a mystery. The early theories of anaesthesia concentrated on a unitary mechanism; however, many recent investigations emphasize specific interactions between anaesthetic agents and excitable membranes. In this study volatile anaesthetics (halothane, isoflurane, enflurane and diethyl ether) applied as vapours in clinical concentrations were observed to produce differential effects on the discharge activity of an isolated crayfish neurone. In addition, both enflurane and diethyl ether induced bursts of discharge activity at concentrations known to produce EEG seizure activity in animals and man. These observations do not support the concept of a common non-specific mechanism of action, but provide further evidence that the action of volatile anaesthetics is selective and may involve multiple sites or mechanisms, or both.