Sex and ovarian hormone cycles alter effects of stimulant drugs on mouse dopaminergic signaling.

Stimulant medications are widely prescribed for attention deficit hyperactivity disorder (ADHD) and have significant abuse liability. Here, we show that, consistent with clinical data, female mice exhibited enhanced behavioral sensitivity to stimulants, and we define sex- and hormone-dependent adaptations in the dopamine system that contributed to these effects. Single-nucleus RNA-seq of ventral tegmental area dopamine neurons revealed that projections to the nucleus accumbens (NAc) core, compared with other projection populations, were a hub of sexually dimorphic gene expression, including transcripts regulating dopamine synthesis, and transport. These molecular differences coincided with enhanced dopamine release and clearance in female mice, particularly during phases of the estrous cycle when estradiol levels were high. The stimulants amphetamine (a releaser) and methylphenidate (a reuptake inhibitor) more effectively increased dopamine levels in female mice under certain conditions. However, amphetamine showed more robust hormone-sensitive regulation, with potency reduced by ovariectomy and restored by direct estradiol replacement in the NAc core. Together, the findings indicate that even within a drug class, drugs with different mechanisms of action can leverage different aspects of sexually dimorphic dopamine function. This distinction highlights the notion that sex differences are not uniform but can be differentially sensitive to drug pharmacology.