ENVIRONMENT AND UNCONDITIONED MOTOR BEHAVIOR - INFLUENCES OF DRUGS AND ENVIRONMENTAL GEOMETRY ON BEHAVIORAL ORGANIZATION IN RATS

Unconditioned motor behavior is widely used as a behavioral assay for a variety of experimental manipulations. This investigation examined t he relationships in rats between effects of drugs (5.0 mg/kg of nomife nsine, 5.0 mg/kg of MBDB, and 0.40 mg/kg of heroin) and the geometric properties of the testing environment (a 30.5 x 60.5 cm rectangular ch amber, a 40-cm-diam circular chamber, and a 60.5 x 60.5 cm square cham ber) using a video-camera-based observation system on measures charact erizing the geometrical characteristics of movements. The results show that spatial patterns of movements differ significantly across enviro nments having different geometric properties. The magnitude of drug-in duced changes of these patterns can be proportional or inversely propo rtional to the baseline rate observed in saline animals. These results suggest that, relative to the performance of saline controls, the eff ect of a drug can be characterized as environmentally dependent, envir onmentally independent., or environmentally idiosyncratic on the basis of its effect in different environments.