CELLULAR MECHANISMS OF GAMMA-RHYTHM IN RAT NEOCORTICAL BRAIN-SLICES PROBED BY THE VOLATILE ANESTHETIC ISOFLURANE

In hippocampus slice preparations, the frequency of gamma oscillations (30-80 Hz) is inversely related to the decay time of GABA(A)-mediated inhibitory postsynaptic currents (IPSCs), suggesting a causal relatio nship [Jefferys, J.R.G., Traub, R.D. and Whittington, M.A., Neuronal n etworks for induced '40 Hz' rhythms, Trends Neurosci., 19 (1996) 202-2 07]. We determined the effects of the commonly used volatile anaesthet ic isoflurane on IPSCs monitored from neocortical and cerebellar neuro ns, as well as on gamma oscillations detected in the field potential o f neocortical brain slices. At 0.16 mM, the anaesthetic lengthened IPS C-decays by a factor of 1.7 and decreased the frequency of gamma oscil lations by 41%. Quantitatively equivalent effects of isoflurane on gam ma rhythms were discovered during encephalographic recordings from hum an patients. (C) 1997 Elsevier Science Ireland Ltd.