Recording oral activity in rats reveals a long-lasting subsensitivity to haloperidol as a function of duration of previous haloperidol treatment

Abstract

Rats pretreated with no drug or with one of two dose levels of continuous haloperidol for 6, 12, or 24 weeks were then given a 5 month drug free interval followed by a single injection of 1 mg/kg haloperidol. Oral movement activity was recorded 2 days before and 7 days after the acute injection of haloperidol using a computerized scoring apparatus. Whereas prior to the acute injection there were no differences between groups, postinjection scores indicated a linear response curve, with the animals which had the least time of exposure showing the greatest increases in oral movement behavior. These data indicate that duration of treatment is a more important factor than is dose level in the development of persistent changes in dopamine-mediated oral activity.