Mecamylamine attenuates ephedrine-induced hyperactivity in rats.

Ephedrine is a central nervous system stimulant that has a pharmacological profile similar to amphetamines. Ephedrine induces hyperactivity after acute administration to rats and locomotor sensitization develops to ephedrine with repeated administration. Recent research suggests that nicotinic receptors (nAChRs) play a role in the development of locomotor sensitization to d-amphetamine and the goal of the present study was to determine if nAChRs similarly mediate the effects of ephedrine after acute and repeated drug injection. On 12 consecutive days, rats were pretreated with the nAChR antagonist mecamylamine (0.3-3.0 mg/kg) or saline followed by (-)-ephedrine (10-30 mg/kg) or saline injection and locomotor activity was measured. Ephedrine produced a dose-dependent increase in locomotor activity, and sensitization to ephedrine developed with repeated injection. Mecamylamine pretreatment attenuated the hyperactivity and sensitization produced by repeated, but not acute, ephedrine (10 mg/kg) injection. The inhibitory effect of mecamylamine was overcome at the higher ephedrine dose (30 mg/kg). The present results indicate that nAChRs play a mediating role in the development of locomotor sensitization to ephedrine.