The effects of n-alcohols on evoked synaptic potentials in rat hippocampal slices: Hill coefficients account for the cut-off phenomenon

The anesthetic potencies of n-alcohols increase progressively with lengthening of the carbon chain and then disappear at a cut-off point of a longer-chain n-alcohol. In order to assess the mechanisms for cut-off in mammalian central nervous system, the effects of a series of n-alcohols (C₂- C₁₁) were examined on the evoked synaptic potentials of the rat hippocampal preparation in vitro. The n-alcohols (C₂-C₁₀) reduced the slope of the excitatory post-synaptic potential in a concentration-dependent manner, and the inhibitory potencies enhanced as a function of carbon chain length. The effect disappeared at n-undecanol (C₁₁). The Hill coefficients of the concentration-response curves of the n-alcohols negatively correlated with the number of carbon atoms. The decrease in the Hill coefficient could account for the cut-off phenomenon, indicating that the results can support the anesthetic pocket hypothesis. (C) 2000 Elsevier Science Ireland Ltd.