Repeated Exposure to beta-phenylethylamine Produces Locomotor Sensitization to Amphetamine, but Not Vice Versa, in the Rat

ABSTRACT

Repeated administration of amphetamine (AMPH) produces behavioral sensitization, a proposed model for the escalation of drug use characteristic of human addicts. beta-Phenylethylamine (PEA) is an endogenous trace amine found in mammalian brain and resembles AMPH both structurally and behaviorally. Previously, it has been reported that chronic PEA administration produces behavioral sensitization to the challenges of AMPH. However, these data were obtained with very high amount of PEA for a relatively long period of time. Further, the effect of PEA challenge on the expression of behavioral sensitization developed by AMPH pre-exposures has not been tested yet. Thus, we examined in the present experiment the expression of behavioral sensitization with AMPH challenge after a mild chronic PEA treatment. Rats were repeatedly administered with systemic injections of saline, beta-phenylethylamine (PEA) (10 or 50 mg/kg), or amphetamine (AMPH) (1.5 mg/kg). When challenged a week after the last pre-injection, rats pre-exposed to either PEA or AMPH showed behavioral sensitization to AMPH (1.0 mg/kg), while these effects were not observed to PEA (50 mg/kg) itself. These results demonstrate that repeated exposure to PEA produces behavioral sensitization to AMPH challenge, while PEA challenge has no effect on the expression of behavioral sensitization developed by AMPH pre-exposures, suggesting that PEA may play a role in the development of locomotor sensitization to AMPH, but not in the expression of it.