EVIDENCE THAT CHANGES IN HIPPOCAMPAL EXCITABILITY IN VITRO ARE CAUSED BY WITHDRAWAL FROM CHRONIC IN VIVO ETHANOL ADMINISTRATION

A complex pattern of changes in the field potentials recordedfrom mouse hippocampal slices, prepared after chronic ethanoltreatment in vivo, has previously been demonstrated in thislaboratory. In the present study, recordings from slices preparedimmediately after 2 weeks of ethanol treatment, showed onlyan increase in paired pulse potentiation, compared with controls,whereas recordings made immediately after 16 weeks of ethanoladministration showed decreases in the thresholds for singleand multiple population spikes, increases in paired pulse potentiationand epileptiform activity. In hippocampal slices prepared after24 hr withdrawal, following 16 weeks of ethanol treatment, therewere no signs of hyperexcitability in the field potentials.Ratings of convulsive behaviour were increased in mice duringa 12-hr period after withdrawal from 16 weeks of ethanol treatment.Corresponding behaviour ratings for the mice given ethanol for2 weeks, or those withdrawn for 24 hr after 16 weeks ethanoltreatment, were not significantly different from control values.It was concluded that epileptiform activity seen in hippocampalslices after prolonged ethanol administration may contributeto the ethanol withdrawal hyperexcitability seen in vivo.