Abstract
A key response to acute stress is the increased brain synthesis of the neurosteroid allopregnanolone (AP). Although the rate-limiting step of this reaction is catalyzed by 5α-reductase (5αR), the role of its two primary isoenzymes, 5αR1 and 5αR2, in stress reactivity remains unclear. Here, we found that acute stress led to increased levels of 5αR2, but not 5αR1, in the medial prefrontal cortex (mPFC) of male, but not female, rats. Down-regulation of 5αR2 in the mPFC significantly reduced stress response in males, and similar sexual dimorphic effects were observed in a novel line of 5αR2 knockout rats. Notably, 5αR1 regulated baseline AP synthesis, whereas 5αR2 enabled AP production under stress. Acute AP administration restored stress response in 5αR2 knockdown rats. Single-nucleus transcriptomics showed that 5αR2 enabled stress-induced protein translation in neurons and glia. These results highlight the crucial role of 5αR2 in mediating sex-specific differences in acute stress reactivity.