Multiple cellular and subcellular actions of general anaesthetics on cultured molluscan neurones.

The pond snail Lymnaea stagnalis has been used as a model system to study the cellular and subcellular actions of general anaesthetics. Here we describe the actions of general anaesthetics mainly on cultured, identified neurones, maintained in isolation to prevent the actions of synaptic inputs upon them. Using the whole-cell patchclamp technique, we have found that application of clinical concentrations of inhalational anaesthetics (halothane and isoflurane) and barbiturates depresses whole-cell calcium currents and potassium currents in a concentration-dependent manner. After loading cultured neurones with the ratiofluorescent dye fura-2AM, we find that halothane raises intracellular calcium concentration in a concentration-dependent manner, both in the presence and absence of extracellular calcium. Thus anaesthetics have multiple cellular and subcellular actions, some of which we have described, but most of which are yet to be discovered.