In rats trained to distinguish ibogaine from a placebo, the metabolite noribogaine produced the same discriminative effect as ibogaine but at roughly half the dose. Noribogaine was found in blood and brain tissue after either ibogaine or noribogaine was given. At doses that produced the discriminative effect, noribogaine concentrations in plasma, cerebral cortex, and striatum were similar whether ibogaine or noribogaine was administered. The findings suggest noribogaine may lack the NMDA antagonist and kappa-opioid agonist effects of ibogaine and may be primarily responsible for ibogaine's discriminative stimulus effect in rats.
Ibogaine, a naturally occurring psychoactive alkaloid reported to block nicotinic receptors, was tested for its ability to alter sensitization to nicotine's locomotor stimulant effect in rats. Over 21 days, rats received daily co-administration of ibogaine (0, 5, or 10 mg/kg) with nicotine (0 or 0.4 mg/kg). Nicotine alone produced clear sensitization—enhanced locomotor activity upon repeated exposure—but co-administration of ibogaine did not affect the degree of sensitization. Ibogaine alone (5–20 mg/kg) did not influence locomotor activity and did not alter the expression of the already-sensitized response to nicotine. The results provide no evidence that ibogaine retards or suppresses sensitization to nicotine.