Low-normal doses of methiopropamine induce aggressive behaviour in mice

Recreational use of illicit methiopropamine (MPA) is a public health concern because it produces neurochemical effects comparable with those induced by methamphetamine (METH). The present study investigated the effects of MPA on the expression of an aggressive behaviour. Eighty CD-1 male mice, after receiving intraperitoneal injection of saline, MPA (0.01–10 mg/kg), METH (0.01–10 mg/kg), or AMPH (0.01–10 mg/kg), once a week over a 5-week period, underwent the resident–intruder test and spontaneous locomotor activity measurement. Results showed that all psychostimulants induce aggressive behaviour even at low doses, with a dose-dependent increase and a time-dependent sensitisation. MPA potency was similar to METH and superior to AMPH. Therefore, MPA-induced aggressive behaviour may appear even at MPA dosages free of cardiovascular or other behavioural adverse effects and could become a non-intentional side effect that users experience after increasing and repeating MPA consumption.