Validation of a photobeam system for assessment of motor activity in rats

To evaluate the validity and sensitivity of test procedures for routine assessment of chemically induced changes in motor activity in rats, studies were carried out with a commercially available photocell cage system. Testing of single, untreated rats showed that motor activity decreased within 10 min to a steady level. Overall activity was the same when testing was repeated at weekly intervals for 6 weeks. In groups of each 10 rats tested immediately after i.p. injection, chlorpromazine HCl (6 or 2 mg/kg) and physostigmine salicylate (0.5 mg/kg) decreased activity. d-Amphetamine sulfate (1.0 mg/kg) caused an increase of virtually all parameters, whereas scopolamine HCl (1.0 mg/kg) and physostigmine salicylate (0.02 mg/kg) led to an increase of particular aspects of motor activity only. Data generated with a mechanical calibrator varied 1-5% between the cages tested. It is concluded that the above procedures of recording of selected parameters of motor activity in groups of 10 rats for periods of up to 20 min would comply with the guidelines recommended by EPA TOSCA.