Acutely administered clozapine does not modify naloxone-induced withdrawal jumping in morphine-dependent mice.

A direct comparison of the effects of clozapine and haloperidol upon naloxone-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 mg/kg s.c., n=9-10) nor haloperidol (0.01-04).1 mg/kg s.c., n=9-10) affected withdrawal jumping precipitated by 0.1 or 15.0 mg/kg i.p. naloxone in morphine-dependent mice. Measurement of locomotor activity immediately prior to naloxone administration revealed a dose-dependent reduction in activity by both compounds, indicating pharmacological effects at the time of naloxone-induced withdrawal. Clonidine (0.02-0.5 mg/kg s.c., n=9-10) also had no affect upon withdrawal jumping, although reductions in locomotor activity prior to naloxone administration were detected. There is no difference in the effects of acutely administered clozapine and haloperidol upon naloxone-precipitated withdrawal jumping in morphine-dependent mice.