Environmental stimulation promotes recovery from haloperidol-induced extinction of open field behavior in rats

Rats receiving 0.1 mg/kg haloperidol showed a progressive decline in their rate of spontaneous motor activity in an open field environment, suggesting that incentive motivational properties of stimuli in the experimental situation may be blunted by neuroleptic treatment. After removal for a short time-out in the home cage they were re-tested in this, or a novel stimulus environment, for a second observation session. Under novel (but not familiar) stimulus conditions haloperidol-treated rats showed an enhancement of spontaneous activity, similar to that observed in vehicle-treated animals, and exceeded their previous low rates of crossing and rearing responses. As drug conditions were similar for the two haloperidol groups, it is likely that neuroleptic-induced effects on spontaneous motor behavior are sensitive to the stimulus complexity of the environmental situation.