Ibogaine enhances the expression of locomotor sensitization in rats chronically treated with cocaine

Pretreatment (19 h) with the putative antiaddictive agent, ibogaine, has be en shown previously to potentiate cocaine-induced locomotion in rats. The p resent study demonstrates that the magnitude of this effect of ibogaine is dependent on the previous cocaine history of the animal, on the time follow ing ibogaine treatment, and on the number of ibogaine treatments. Compared to rats with no previous cocaine experience, ibogaine pretreatment (40 mg/k g, IP, 19 h earlier) markedly enhanced the expression of locomotor sensitiz ation in response to a cocaine challenge injection (7.5 mg/kg) in rats that were chronically treated with cocaine (15 mg/ kg, IP, daily for 5 days). T olerance to cocaine-induced locomotor sensitization appeared to occur in ve hicle-pretreated chronic cocaine controls. Following a second series of ide ntical treatments (beginning 3-4 days after the initial treatment series), locomotor responding to the cocaine challenge was further enhanced by a sec ond ibogaine injection in chronically cocaine-treated animals. Twenty-four hours later, when animals were challenged again with cocaine in the absence of any further ibogaine pretreatment, the effect of ibogaine had dissipate d. Consistent with previous studies from this laboratory, these data demons trate that ibogaine can enhance sensitivity to the psychomotor stimulant ef fect of cocaine. The results of the present study further indicate that the extent of this effect depends on the animal's history of exposure to both ibogaine and cocaine. (C) 1999 Elsevier Science Inc.