Metabolic turnover in the reticular activating system in ammonia induced coma.

Previous studies have implicated the ascending reticular activating system (RAS) as playing a vital role in ammonia induced coma. It has been shown, for example, that cells of the RAS have selective decreases in the level of energy metabolites such as ATP and phosphocreatine as compared to adjacent tissue during ammonia induced encephalopathy. To determine the utilization rate of metabolites during ammonia induced coma, we have examined the turnover rate of four key energy metabolites in 20-22 gram mice. Results from this study show decreases in the turnover of glucose, glycogen, and phosphocreatine. The derived value for the turnover of energy metabolites was decreased by 49% as compared to that of control mice. These data suggest that energy utilization is decreased at a time when the physiological output of the RAS is also diminished and the animal is comatose.