Cerebral Acetylcholine, Serotonin, and Norepinephrine in Acute Ammonia Intoxication (35336)

The primary purpose of this study was to assess the hypothesis that a depletion of cerebral acetylcholine (ACh) may be responsible for the coma induced with ammonia. An ancillary aim was to determine the effect of ammonia on cerebral levels of two other likely neurotransmitters, serotonin and norepinephrine. Acetylcholine, serotonin, and norepinephrine were measured in the brain of rats with NH₄Ac-induced stupor and in asympotomatic NaAc-injected and uninjected controls. Studies were carried out during and after the development of stupor; and both cortex and brainstem were assayed separately since these areas are believed to be primarily responsible for the maintenance of consciousness. Acetylcholine was measured by a specific and accurate fluorometric procedure. In rats with ammonia-induced precoma and coma, the ACh and norepinephrine levels in the cerebral cortex and brainstem were comparable to values seen in control animals. Cerebral serotonin likewise was normal during the development of stupor but fell modestly in both cortex and brainstem of animals with established coma. This study indicates that cerebral regional stores of ACh, serotonin, and norepinephrine are normal during the development of acute ammonia-induced coma and that other mechanisms for this neurologic dysfunction will have to be considered.