Bidirectional sex-dependent regulation of α6 and β3 nicotinic acetylcholine receptors by protein kinase Cε

Nicotine and alcohol are the most commonly abused substances worldwide, and comorbid nicotine and alcohol addiction is highly prevalent. Nicotinic acetylcholine receptors (nAChRs) containing the α6 and β3 subunits are expressed in neural reward circuits and are critical for both nicotine and alcohol reward. nAChRs are dynamically regulated by signaling molecules such as protein kinase C epsilon (PKCε), which impact transcription of α6 and β3 subunit mRNA (Chrna6 and Chrnb3, respectively). Previous work found decreased expression of Chrna6 and Chrnb3 transcripts in the ventral midbrain of male PKCε−/− mice, who also consume less nicotine and alcohol compared to wild-type (WT) littermates. Here, we show that female PKCε−/− mice have enhanced expression of Chrna6 and Chrnb3 transcripts in the ventral midbrain, which functionally impacts nAChR-dependent behavior, as female but not male PKCε−/− mice exhibit locomotor hypersensitivity to nicotine. Female PKCε−/− mice show no differences in alcohol-induced sedation compared to WT littermates, while male PKCε−/− have enhanced sedation compared to WT mice, a phenotype that has previously been reported in α6−/− mice. Female PKCε−/− mice also show reduced depression-like behavior in response to systemic injections of varenicline compared to WT littermates, and this effect was absent in male mice. Additionally, we found that female PKCε−/− mice show altered alcohol and nicotine consumption patterns in chronic voluntary two bottle choice assays. Our data reveal a bidirectional effect of sex in the transcriptional regulation of nicotinic receptors by PKCε, and highlight the importance of studying both sexes in preclinical animal models.