Pharmacology of novel synthetic stimulants structurally related to the 'bath salts' constituent 3,4-methylenedioxypyrovalerone (MDPV)
There has been a dramatic rise in the abuse of synthetic cathinones known as 'bath salts,' including 3,4-methylenedioxypyrovalerone (MDPV), an analog linked to many adverse events. MDPV differs from other synthetic cathinones because it contains a pyrrolidine ring which gives the drug potent actions as an uptake blocker at dopamine and norepinephrine transporters. While MDPV is now illegal, a wave of 'second generation' pyrrolidinophenones has appeared on the market, with alpha-pyrrolidinovalerophenone (alpha-PVP) being most popular. Here, we sought to compare the in vitro and in vivo pharmacological effects of MDPV and its congeners: alpha-PVP, alpha-pyrrolidinobutiophenone (alpha-PBP), and alpha-pyrrolidinopropiophenone (alpha-PPP). We examined effects of test drugs in transporter uptake and release assays using rat brain synaptosomes, then assessed behavioral stimulant effects in mice. We found that alpha-PVP is a potent uptake blocker at dopamine and norepinephrine transporters, similar to MDPV. alpha-PBP and alpha-PPP are also catecholamine transporter blockers but display reduced potency. All of the test drugs are locomotor stimulants, and the rank order of in vivo potency parallels dopamine transporter activity, with MDPV > alpha-PVP > alpha-PBP > alpha-PPP. Motor activation produced by all drugs is reversed by the dopamine receptor antagonist SCH23390. Furthermore, results of a functional observational battery show that all test drugs produce typical stimulant effects at lower doses and some drugs produce bizarre behaviors at higher doses. Taken together, our findings represent the first evidence that second generation analogs of MDPV are catecholamine-selective uptake blockers which may pose risk for addiction and adverse effects in human users. This article is part of a Special Issue entitled 'CNS Stimulants'