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 - females exhibit enhanced behavioral sensitivity to stimulants and define sex- and hormone-dependent adaptations in the dopamine system that contribute to these effects. Single-nucleus RNA sequencing of ventral tegmental area dopamine neurons revealed that projections to the nucleus accumbens (NAc) core - compared to 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 females, 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 females 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 that sex differences are not uniform but can be differentially sensitive to drug pharmacology.