Estrous cycle influences cell-type-specific translatomic signatures of repeated ketamine exposure in the rat nucleus accumbens

The growing therapeutic promise of repeated, low-dose ketamine treatment across various psychopathologies-including depression and drug addiction-warrants clarity on its potential addictive properties and their associated mechanisms in both sexes. Accordingly, the present work examined the effects of repeated low-doses ketamine in male and female rats on behavioral sensitization to the locomotor activating effects of ketamine, as well as the associated molecular profiles in dopamine D1- and D2-receptor-expressing medium spiny neurons (D1- and D2-MSNs) of the nucleus accumbens (NAc). Following intra-NAc infusion of a Cre-inducible RiboTag virus, locomotor activity was measured in adult Drd1a-iCre and Drd2-iCre male and female rats in either diestrus or proestrus following repeated administration of ketamine (0, 10, or 20 mg/kg, i.p.) to evaluate the development of locomotor sensitization. Female-but not male-rats developed sensitization to the locomotor-activating effects of ketamine, occurring more rapidly in proestrus than in diestrus females at the lower dose tested. To examine enduring context- and cell-type-specific changes in translating mRNAs associated with sensitization to ketamine, RNA sequencing was performed on polyribosome-bound mRNA of D1- and D2-MSNs isolated from the NAc of sensitized females in a drug-free state. A greater number of differentially expressed genes were observed selectively in D1-MSNs of ketamine-treated proestrus compared to diestrus females, which were broadly related to regulation of transcription and epitranscriptional modification. These findings provide novel evidence of cell-type-specific and estrous-cycle-dependent molecular profiles responsive to intermittent ketamine treatment in female rats and identify post-transcriptional mechanisms with relevance to ketamine's effects on behavioral plasticity. Overall design: RNA-seq profiling of total RNA extracted from RiboTag-immunoprecipitated (IP) polyribosomes in nucleus accumbens tissue punches collected from female Drd1a-iCre and Drd2-iCre Long Evans rats receiving intermittent ketamine (10 mg/kg, i.p., 6 injections 4-5 days apart) or saline (i.p., 6 injections 4-5 days apart) in the proestrus or diestrus phase of the estrous cycle.