Effects of abrupt and gradual withdrawal from long-term haloperidol treatment on open field behavior of rats.

The effects of abrupt and gradual withdrawal from long-term haloperidol treatment on rat open field behavior was studied. Abrupt withdrawal induced a significant increase in all parameters of activity observed except defecation, this increase being higher 72 h after the last haloperidol injection. Results were considered to be a consequence of supersensitivity of central dopaminergic receptors. These differences were almost unobservable in animals gradually withdrawn, thus suggesting that the phenomenon is reversible.