Tremorous mouth movements in rats administered chronic neuroleptics

Oral movements (OMs) in rats administered chronic haloperidol (HAL) were quantified simultaneously by a human observer and via a computerized video analysis system which monitored the distance between the upper and low lips using TV images. The human observer data indicated that during HAL administration the total duration of OMs was initially decreased, gradually returned to levels slightly above controls, and then increased substantially upon drug withdrawal. The computer records confirmed these findings and further indicated that after prolonged HAL administration a syndrome developed in which large-amplitude OMs remained suppressed but OMs of the smallest detectable amplitudes increased. Upon drug withdrawal, these small OMs increased in amplitude and rhythmicity, developing into repetitive tremors.