Visual evoked potentials in a rabbit model of hepatic encephalopathy. I. Sequential changes and comparisons with drug-induced comas.

The recording of visual evoked potentials in rabbits has been shown to be an objective, reproducible, noninvasive technique for quantitating changes in the pattern of cerebral neuronal activity. The development of hepatic encephalopathy due to galactosamine-induced fulminant hepatic failure was consistently associated with a series of distinctive changes in the visual evoked potential waveform. The pattern of the visual evoked potential in hepatic coma (due to galactosamine-induced fulminant hepatic failure) differed fundamentally from that in ether-induced coma, but was identical to that in comas induced by three drugs which activate gamma-aminobutyric acid-ergic neural mechanisms: pentobarbital, diazepam, and muscimol. These findings are compatible with activation of the gamma-aminobutyric acid inhibitory neurotransmitter system contributing to cerebral neuronal inhibition in hepatic coma due to galactosamine-induced fulminant hepatic failure.