Abstract
In recent years, synthetic analogues of naturally occurring cathinone have emerged as psychostimulant-like drugs of abuse in commercial 'bath salt' preparations. 3,4-Methylenedioxypyrovalerone (MDPV) is a common constituent of these illicit products, and its structural similarities to the more well-known drugs of abuse 3,4-methylenedioxymethamphetamine (MDMA), and methamphetamine (METH) suggest that it may have similar in vivo effects to these substances. In these studies, adult male NIH Swiss mice were trained to discriminate 0.3 mg/kg MDPV from saline, and the interoceptive effects of a range of substitution doses of MDPV, MDMA, and METH were then assessed. In separate groups of mice, surgically implanted radiotelemetry probes simultaneously monitored thermoregulatory and locomotor responses to various doses of MDPV and MDMA, as a function of ambient temperature. We found that mice reliably discriminated the MDPV training dose from saline and that cumulative doses of MDPV, MDMA, and METH fully substituted for the MDPV training stimulus. All three drugs had similar ED(50) values in this procedure. Stimulation of motor activity was observed following administration of a wide range of MDPV doses (1-30 mg/kg), and the warm ambient temperature potentiated motor activity and elicited profound stereotypy and self-injurious behavior at 30 mg/kg. In contrast, MDPV-induced hyperthermic effects were observed in only the warm ambient environment. This pattern of effects is in sharp contrast to MDMA, where ambient temperature interacts with thermoregulation, but not locomotor activity. These studies suggest that although the interoceptive effects of MDPV are similar to those of MDMA and METH, direct effects on thermoregulatory processes and locomotor activity are likely mediated by different mechanisms than those of MDMA.