N-Isopropylbenzylamine-induced conditioned place preference, sensitization behaviour and self-administration in rodents

Abstract

N-Isopropylbenzylamine (N-ipb), a chain isomer of methamphetamine (METH) with similar physical properties, has been used as a substitute for METH in seized drug samples. However, the abuse potential of N-ipb remains unclear. Therefore, this study aimed to evaluate the abuse potential of N-ipb in comparison to METH, by using conditioned place preference (CPP), locomotor sensitization and intravenous self-administration tests. The results showed that N-ipb at a dose of 3 mg·kg⁻¹ significantly induced CPP in mice, which was comparable to the effect of METH at 1 mg·kg⁻¹. Either acute or repeated N-ipb injections (1 or 3 mg·kg⁻¹) failed to raise the locomotor activity. However, acute treatment with 10 mg·kg⁻¹ N-ipb elevated the locomotor activity compared with saline, while chronic injection of 10 mg·kg⁻¹ N-ipb induced a delayed and attenuated sensitization compared with 1 mg·kg⁻¹ METH. Rats could acquire N-ipb self-administration at a dose of 1 mg·kg⁻¹·infusion⁻¹, and a typical inverted U-shaped dose–response curve was obtained for N-ipb. The mean dose of N-ipb that maintained the maximum response was greater than that of METH, indicating that N-ipb is less potent for reinforcement than METH. In the economic behavioural analysis, comparison of essential values derived from the demand elasticity revealed that N-ipb is less efficacy as a reinforcer than METH. The present data demonstrate that N-ipb functions as a reinforcer and has a potential for abuse. However, the potency of psychomotor stimulation and the reinforcing effectiveness of N-ipb are lower than those of METH.