Estrogen Receptor Beta Localized on Ventral Tegmental Area Dopamine Neurons Regulates Nicotine Self-Administration Acquisition in Ovary-Intact Female Rats

Women exhibit greater nicotine use vulnerability than men. High estradiol (E2) exacerbates nicotine use outcomes in women, effects which have been modeled in preclinical nicotine self-administration (SA) studies. Nicotine SA is maintained by dopamine (DA) release from the ventral tegmental area (VTA) to the nucleus accumbens (NA). E2 exerts its effects by binding to estrogen receptors (ER), including ERα, ERβ, and G-protein coupled ER-1 (GPER-1)s. E2 action at ERs specifically has been shown to potentiate DA neuronal excitability within the VTA. Further, we have shown that ovariectomy decreases both nicotine use during SA and VTA ERβ protein. Despite clear evidence of mechanistic relationships between E2, ERs, DA, and nicotine, no studies to date have functionally evaluated the specific role of ERβ located on VTA DA cells in driving nicotine consumption during SA in females. There are currently no tools that allow for evaluations of relationships between nicotine neurobiology and ERs with cell-type specificity, as ERβ is also localized on other (non-DA) cell types within the VTA. As such, the goals of the present studies were (1) to build and validate a novel adeno-associated viral construct that produces long-term knockdown of ERβ specifically on VTA DA neurons, and (2) to determine if VTA DA ERβ viral knockdown reduces nicotine SA in ovary-intact female rats. Here we show that ERβ regulates VTA DA neuron excitability, and that ERβ knockdown in VTA DA neurons reduces DA neuron firing frequency. We also show that VTA ERβ knockdown in DA neurons reduces nicotine SA acquisition in ovary-intact female rats. Together, our results demonstrate a critical role of ERβ in driving nicotine use in females, underscoring the need for future studies to evaluate neurobehavioral mechanisms of smoking through the lens of sex differences.