OBJECTIVE: The aim of the study was to find how a simultaneous impairment of the CNS (cellular brain edema induced by water intoxication) and PNS (blockade of the right forelimb brachial plexus by local anesthewtic - Marcaine) affects spontaneous locomotor activity of adult rats. METHODS: Rats were divided into groups of animals without water intoxication (without WI) - A,B,C, and those that were water intoxicated (induction of brain edema - after WI) - D,E,F. Both groups were further divided into intact ones (A,D), animals with PNS lesion (Marcaine) (B,E) and sham-operated animals (C,F). Locomotor activity (LA) of the rats was tested by the open field test. RESULTS: LA of rats with both CNS and PNS impairment (WI + Marcaine) was significantly suppressed compared to the activity of control rats. Comparison of LA of rats with a single lesion - PNS impairment only (Marcaine only), CNS lesion only (WI) to those animals with both lesions (WI + Marcaine) revealed even larger decrease of LA of rats with combined lesions, which represents a model of the dual diagnosis. Also the pattern of behaviour of rats in both sham operated groups was different, which apparently depended on water intoxication. CONCLUSION: The presented results show that the LA of rats with combined lesions is significantly lower compared to the activity of rats with a single lesion in the CNS or PNS. Results also indicate that the already induced endoneurial edema prevents subsequent accumulation of water applied to the intimate vicinity of the peripheral nervous structures.