Behavioral and biochemical changes following repeated administration of carbaryl to aging rats.

Motor, sensory and thermoregulatory functions were examined in aging rats (12 months) following two schedules of repeated po administration of the carbamate insecticide carbaryl and these effects were assessed in terms of blood cholinesterase activity. Administration of carbaryl (50 mg/kg) by gavage daily for 30 days resulted in a reduction of locomotor activity in the open-field and in an inhibition of cholinesterase activity within 30 min after the last treatment. Twenty-four h later, only the locomotor effect was evident. After 90 days of exposure to carbaryl in drinking water, no significant effects were observed. These findings suggest that repeated administration of carbaryl to aging rats can induce an impairment of motor function and a reduction of cholinesterase activity, while tolerance develops in some other parameters.