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

Abstract

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 6 and {beta}3 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 (PKC{varepsilon}), which impact transcription of 6 and {beta}3 subunit mRNA (Chrna6 and Chrnb3, respectively). Previous work found decreased expression of Chrna6 and Chrnb3 transcripts in the ventral midbrain of male PKC{varepsilon}-/- mice, who also consume less nicotine and alcohol compared to wild-type (WT) littermates. Here, we show that female PKC{varepsilon}-/- mice have enhanced expression of Chrna6 and Chrnb3 transcripts in the ventral midbrain, which functionally impacts nAChR-dependent behavior, as female but not male PKC{varepsilon}-/- mice exhibit locomotor hypersensitivity to nicotine. Female PKC{varepsilon}-/- mice show no differences in alcohol-induced sedation compared to WT littermates, while male PKC{varepsilon}-/- have enhanced sedation compared to WT mice, a phenotype that has previously been reported in 6-/- mice. Female PKC{varepsilon}-/- 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 PKC{varepsilon}-/- 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 PKC{varepsilon}, and highlight the importance of studying both sexes in preclinical animal models.