Comparative evaluation of visual evoked potentials in experimental hepatic encephalopathy and in pharmacologically induced coma-like states in rat

Visual Evoked Potential (VEP) was used as a method for the evaluation of Hepatic Encephalopathy (HE) in rats with galactosamine induced Fulminant hepatic Failure (FHF). Two degrees of the coma were documented by two different patterns in VEP recording. Animals under pentobarbital anaesthesia had a VEP waveform clearly different from the coma VEP and, as a further demonstration of the specificity in VEP changes, Amino-oxyacetic acid produced a VEP waveform similar to that due to pentobarbital anaesthesia. Neither ammonia nor amino acids (tryptophan and phenylalanine), believed to be inducers of HE-like neurological symptoms in normal animals, produced a VEP waveform similar to VEP recorded during HE. The authors propose this method for the evaluation, quantification and documentation of the neurological changes during experimental HE and during experiments inducing a HE-like state in normal animals.