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Neuropharmacology. 2003 Jun;44(7):864-72.

The effects of general anaesthetics on carbachol-evoked gamma oscillations in the rat hippocampus in vitro.

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Biophysics Group, Imperial College of Science, Technology & Medicine, Blackett Laboratory, Prince Consort Road, London SW7 2BW, UK.


The effects of general anaesthetics and temperature on carbachol-evoked gamma oscillations in the rat hippocampal brain slice preparation were investigated. The frequency of the oscillations was found to be dependent on temperature in the range 32-25 degrees C, with a linear reduction in frequency from 40-17 Hz over this temperature range. The volatile anaesthetics isoflurane and halothane, and the intravenous anaesthetics thiopental, propofol and R(+)-etomidate caused a reduction in the frequency of the oscillations, in a concentration-dependent manner, over a range of clinically relevant concentrations. On the other hand, the intravenous agent ketamine and the "inactive" S(-)-isomer of etomidate had no significant effect on the oscillation frequency. The oscillations were markedly asymmetric over one cycle with a relatively rapid "rising" phase followed by a slower "decaying" phase. The decrease in oscillation frequency was due to an increase in the time-course of the "decaying phase" of the oscillation with little effect on the "rising" phase, consistent with the idea that carbachol-evoked gamma oscillations are trains of GABAergic inhibitory postsynaptic potentials and that the anaesthetics are acting postsynaptically at the GABA(A) receptor.

[Indexed for MEDLINE]

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