The action of general anaesthetics on acetylcholine-induced inhibition in the central nervous system of Helix.

The effects of general anaesthetics, thiopentone, etomidate, minaxolone and ketamine were studied on identified voltage-clamped neurones of Helix aspersa. At concentrations of 0.1-0.5 mM, thiopentone, etomidate and minaxolone had no effect on the resting conductance of identified cells, D1 and D2. Ketamine at a concentration of 0.1-0.5 mM depolarized and excited the cells. All four anaesthetics tested depressed a chloride-dependent inhibitory response to acetylcholine (ACh) in cells D1 and D2 at concentrations of 0.1-0.5 mM in a dose-dependent and reversible manner with no change in the reversal potential of the response. These results show that general anaesthetics can block the transmitter-evoked chloride-mediated increases in membrane conductance in Helix neurones.