Contrasting effects of d-methamphetamine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxypyrovalerone, and 4-methylmethcathinone on wheel activity in rats

Summary

Recreational use of the synthetic cathinones mephedrone (4-MMC) and MDPV is increasing, with reports of severe symptoms and deaths, but laboratory research on their effects is limited. In male Wistar rats, MDPV and methamphetamine produced a biphasic pattern of voluntary wheel running—higher activity at low doses and lower activity at the highest dose—while 4-MMC and MDMA caused dose-dependent reductions in activity. These results mirror the drugs' known effects on dopamine and serotonin neurotransmission, suggesting MDPV acts as a typical stimulant and 4-MMC resembles the entactogen MDMA, which may predict different abuse patterns and toxicities.

Study at a glance

Abstract

BACKGROUND Reports from US, UK and European drug policy entities, and ongoing media accounts, show increasing recreational use of 4-methylmethcathinone (4-MMC, mephedrone) and 3,4-methylenedioxypyrovalerone (MDPV). Severe sympathomimetic symptoms, hallucinations, psychoses, and even deaths have been reported, yet little scientific information is available on the effects of these compounds in laboratory models. Available studies on the neurochemistry of these drugs show that 4-MMC and MDPV enhance DA neurotransmission, while 4-MMC additionally enhances 5-HT neurotransmission- a pattern much like that reported for methamphetamine vs. 3,4-methylenedioxymethamphetamine (MDMA). As is the case for designer amphetamines, these neurochemical distinctions may predict differential potential for repetitive versus episodic abuse and distinct lasting toxicities. METHODS This study determined relative locomotor stimulant effects of 4-MMC (1–10 mg/kg, s.c.) and MDPV (0.5–5.6 mg/kg, s.c.), in comparison with d-methamphetamine (MA; 0.5–5.6 mg/kg, s.c.) and MDMA (1–7.5 mg/kg, s.c.) on a measure of locomotor activity – voluntary wheel running – in male Wistar rats (N=8). RESULTS Compared to counts of wheel rotations after saline, a biphasic change in the pattern of counts was observed after injections of MA and MDPV, with relatively higher counts following lower doses and lower counts following the highest dose. However, monophasic, dose-dependent reductions in counts were observed in response to injections of MDMA and 4-MMC. CONCLUSION Thus, voluntary wheel running yielded the same categorical distinctions for these drugs as did prior experiments testing the effects of these drugs on monoaminergic neurotransmission. These data indicate that MDPV produces prototypical locomotor stimulant effects whereas 4-MMC is more similar to the entactogen MDMA.