Acutely administered clozapine does not modify naloxone-induced withdrawaljumping in morphine-dependent mice

A direct comparison of the effects of clozapine and haloperidol upon naloxo ne-induced withdrawal jumping was investigated in morphine-dependent mice, as this syndrome may provide a behavioral baseline to differentiate between the two neuroleptics. Neither clozapine (0.03-3.0 mgikg SC, n = 9-10) nor haloperidol (0.01-0.1 mg/kg SC, n = 9-10) affected withdrawal jumping preci pitated by 0.1 or 15.0 mg/kg IP naloxone in morphine-dependent mice. Measur ement of locomotor activity immediately prior to naloxone administration re vealed a dose-dependent reduction in activity by both compounds, indicating pharmacological effects at the time of naloxone-induced withdrawal. Clonid ine (0.02-0.5 mg/kg SC, n = 9-10) also had no affect upon withdrawal jumpin g, although reductions in locomotor activity prior to naloxone administrati on were detected. There is no difference in the effects of acutely administ ered clozapine and haloperidol upon naloxone-precipitated withdrawal jumpin g in morphine-dependent mice. (C) 1998 Elsevier Science Inc.