Comparison of electroencephalogram (EEG) response to MDPV versus the hallucinogenic drugs MK-801 and ketamine in rats

Abstract Synthetic cathinones, often marketed as ‘bath salts’, have been reported to induce an excited delirium syndrome with characteristic symptoms such as paranoid, hallucination and even aggression. 3,4-Methylenedioxypyrovalerone (MDPV), a norepinephrine-dopamine reuptake inhibitor (NDRI), is one of the psychoactive ingredients in bath salts. The present study utilized cortical EEG and brain microdialysis in rats to compare the effects of MDPV (0.25, 1 and 2 mg/kg, i.p.) with the hallucinogenic drugs MK-801 (0.05, 0.1 and 0.5 mg/kg, i.p.) and ketamine (5, 15 and 25 mg/kg, i.p.). Results revealed that MDPV similar to MK-801 and ketamine caused a dose-dependent increase in the cortical EEG synchronization. In addition, all three drugs produced an increase in DA efflux in the prefrontal cortex (FCx). However, there existed difference between the three drugs. In contrast to MDPV, MK-801 and ketamine had only moderate or little effects on DA efflux in the nucleus accumbens (NAcc). Except for ketamine, the effects of MDPV and MK-801 on EEG synchronization were blocked by the D 1 receptor antagonist SCH23990 (0.1 mg/kg, i.p.) and D 2 receptor antagonist sulpiride (100 mg/kg, i.p.). SCH23990 or sulpiride had no effect on ketamine-induced increases in EEG synchronization. In summary, the present comparative studies suggest that DA in the FCx, but unlikely the NAcc, exerts a critical role in increasing EEG synchronization associated with the excited delirium syndrome. Neural circuits consisting of glutamatergic and GABAergic neurons responsible for the hallucinogenic effect are discussed in the context of hyperdopamine and dysconnection theories for hallucinatory behaviors.