EFFECTS OF GINSENG TOTAL SAPONIN ON MORPHINE-INDUCED HYPERACTIVITY AND CONDITIONED PLACE PREFERENCE IN MICE

A single or repeated administration of morphine in mice produced hyper activity, conditioned place preference (CPP) and postsynaptic dopamine (DA) receptor supersensitivity. The hyperactivity induced by morphine was evidenced by measuring the enhanced ambulatory activity using a t ilting-type ambulometer. CPP effects were evaluated assessing the incr eased time spent by the mice to morphine and the inhibition of CPP by the decreased time spent by the mice in the white compartment. Postsyn aptic DA receptor supersensitivity in mice displaying a morphine-induc ed CPP was evidenced by the enhanced response in ambulatory activity t o the DA agonist, apomorphine (2 mg/kg, s.c.). The intraperitoneal inj ection of ginseng total saponin (GTS) from the root of Panax ginseng C .A. Meyer (Araliaceae), prior to and during the morphine treatment in mice inhibited morphine-induced hyperactivity and CPP. GTS inhibited t he development of postsynaptic DA receptor supersensitivity. A single dose administration of GTS also inhibited apomorphine-induced climbing behavior, showing the antidopaminergic action of GTS at the postsynap tic DA receptor. These results suggest that the development of morphin e-induced CPP may be associated with the enhanced DA receptor sensitiv ity and that GTS inhibition of the morphine-induced hyperactivity and CPP may be closely related with the inhibition of dopaminergic activat ion induced by morphine. (C) 1998 Elsevier Science Ireland Ltd.