Striatal Dopamine D2 Receptors Contribute to N-Ethylpentylone-Induced Arousal in Mice

Drug-induced sleep disruption exacerbates addiction, causes long-term cognitive and emotional deficits, and becomes a key relapse trigger. However, despite the potent stimulant and hallucinogenic effects of synthetic cathinones, their impact on sleep-wake behaviors remains unstudied, and the role of striatal dopamine D2 receptors in mediating psychostimulant-induced arousal has yet to be identified. This study aimed to elucidate the mechanisms underlying N-ethylpentylone (NEP, a second-generation synthetic cathinone) induced alterations in sleep-wake behavior, specifically investigating the relative contributions of dopamine receptors (DARs) and serotonin receptors. Using the in vitro PRESTO-Tango assay, we characterized the interactions between NEP and various DARs, revealing that NEP produced the strongest β-arrestin recruitment response at dopamine D2 receptor (D2R) among the dopamine receptor subtypes tested. In vivo electroencephalogram/electromyogram (EEG/EMG) recordings in wild-type (WT) mice demonstrated that NEP dose-dependently promoted wakefulness and reduced non-rapid eye movement (NREM) sleep. This was accompanied by decreased θ-band and increased α-band power spectral density during wakefulness. Pharmacological blockade of D2R with haloperidol significantly attenuated NEP-induced wake promotion and partially reversed the aberrant EEG oscillations. Crucially, conditional knockout of D2R specifically in striatum markedly diminished the wake-promoting effects of NEP. In contrast, pharmacological blockade of the serotonin 2 A receptor (5-HT2AR) with 1 mg/kg MDL100907 did not significantly alter NEP-induced sleep-wake changes. Furthermore, immunofluorescence staining analysis confirmed that D2R blockade effectively reversed NEP-induced c-Fos expression in the striatum. Together, these findings demonstrated striatal D2R played a critical role in NEP-induced arousal.