BEHAVIORAL SUBSENSITIVITY INDUCED BY LONG-TERM ADMINISTRATION OF A LOW-DOSE OF HALOPERIDOL TO RATS

This study examines the effects on open-field and stereotyped behaviou r of rats of abrupt withdrawal from repeated treatment with a low (0.0 3 mg kg(-1)) dose of haloperidol. Single administration of this low do se of haloperidol significantly increased open-field locomotion withou t modifying apomorphine (0.5 or 2.0 mg kg(-1))-induced stereotyped beh aviour. Forty-eight hours after abrupt withdrawal from 0.03 mg kg(-1) haloperidol (twice daily for 15 days) a significant decrease in locomo tion frequency was observed, but no change was observed in apomorphine -induced stereotypy. Our results suggest that dopamine autoreceptor su persensitivity might be evaluated in a behavioural situation of absenc e of postsynaptic dopamine receptor supersensitivity.