Effects of apomorphine administration on locomotor activity of control and experimental rats withdrawn from long-term...

Rats were administered increasing doses of haloperidol or control solution for 25 days, 72 hr after drug withdrawal they were observed for locomotor activity in an open field with and without apomorphine treatment. Locomotion frequency was higher in haloperidol withdrawn rats. In both groups locomotion frequency decreased 15 min after apomorphine administration, in a dose-dependent way. Apomorphine induced, also, different motor effects not necessarily similar in control and experimental rats. Supersensitivity of dopaminergic receptors induced by the long-term neuroleptic administration was considered to be involved with the differences observed.