['Ornithine phenylacetate (OP) is a new drug that has been proposed for the treatment of hepatic encephalopathy (HE) because it decreases plasma ammonia. We performed a study to assess if OP would impact on neuronal function.', 'Motor-evoked potentials (MEP), a surrogate of hepatic encephalopathy, were assessed (without anesthesia) in rats with portacaval anastomosis (PCA) that received gastrointestinal blood (GIB). Rats were pre-treated with OP prior to GIB. Ammonia and related metabolites (plasma, urine, and brain microdialysis) were assessed by HPLC and mass spectroscopy.', 'OP (one dose or 3 days) prevented disturbances in MEP induced by GIB in PCA rats. In rats treated with OP for 3 days, the amplitude and latency of MEP remained stable (-1% and +1%), while in the control group the amplitude decreased -21% and the latency increased +12% (p<0.01). OP attenuated the rise of ammonia in plasma by 45%, ammonia in brain microdialysate by 48%, induced a faster glutamine rise and the appearance of phenylacetylglutamine in plasma and urine. In addition, OP was associated with a lower concentration of ammonia and glutamate in brain microdialysate (approx. 50%).'] Does ornithine phenylacetate prevent disturbances of motor-evoked potentials induced by intestinal blood in rats with portacaval anastomosis?