A toxic dose of ammonium chloride (> 12 mmol/kg) caused death of animals within 10 min of i.p. injection, while pentobarbital--(40 mg/kg, i.p.) and kurare--(0.2 mg/kg, i.v.) injected rats died only in 11% of the tests. At 40 min after the injection of NH4Cl, the kurare-treated animals had minimum EEG amplitude in the cortex, maximum--in RF, and unchanged in amygdala. At the same time evoked potentials (EP) in RF induced by the periphery stimuli remained unchanged in form and increased in amplitude. Corticofugal impulses had no specific influence on the formation of EP in RF. The initial potentials were restored within 3 hrs. Thus, it could be concluded that ammonium differentiatively changed the state of the normal brain functional systems; it increased the afferentation and excitation of RF which could lead to violation of the vitally important functions especially breathing and cause the lethal outcome.