TY - JOUR T1 - Estradiol Drives the Anorexigenic Activity of Proopiomelanocortin Neurons in Female Mice JF - eneuro JO - eNeuro DO - 10.1523/ENEURO.0103-18.2018 SP - ENEURO.0103-18.2018 AU - Todd L. Stincic AU - Pasha Grachev AU - Martha A. Bosch AU - Oline K. Rønnekleiv AU - Martin J. Kelly Y1 - 2018/07/17 UR - http://www.eneuro.org/content/early/2018/07/17/ENEURO.0103-18.2018.abstract N2 - Energy balance is regulated by anorexigenic proopiomelanocortin (POMC) and orexigenic neuropeptide Y/agouti-related peptide (NPY/AgRP) neurons of the hypothalamic arcuate nucleus. POMC neurons make extensive projections and are thought to release both amino acid and peptide neurotransmitters. However, whether they communicate directly with NPY/AgRP neurons is debated. Initially, using single cell RT-PCR, we determined that mouse POMCeGFP neurons express Slc17a6 (Vglut2) and Slc18a2 (Vmat2), but not Slc31a1 (Vgat) mRNA, suggesting glutamate and non-canonical GABA release. Quantitative RT-PCR of POMCeGFP cells revealed that Vglut2 and Vmat2 expression was significantly increased in E2- vs. oil-treated, ovariectomized (OVX) female mice. Since 17β-estradiol (E2) is anorexigenic, we hypothesized that an underlying mechanism was enhancement of POMC signaling. Therefore, we optogenetically stimulated POMC neurons in hypothalamic slices to examine evoked release of neurotransmitters onto NPY/AgRP neurons. Using brief light pulses we primarily observed glutamatergic currents and, based on the paired pulse ratio, determined that release probability was higher in E2- vs oil-treated, OVX female, congruent with increased Vlgut2 expression. Moreover, bath perfusion of the Gq-coupled membrane estrogen receptor agonist STX recapitulated the effects of E2 treatment. In addition, high frequency (20 Hz) stimulation generated a slow outward current that reversed near Ek+ and was antagonized by naloxone, indicative of β-endorphin release. Furthermore, individual NPY/AgRP neurons were found to express Oprm1, the transcript for μ-opioid receptor, and DAMGO, a selective agonist, elicited an outward current. Therefore, POMC excitability and neurotransmission are enhanced by E2, which would facilitate decreased food consumption through marked inhibition of NPY/AgRP neurons.Significance Statement Proopiomelanocortin (POMC) neurons of the hypothalamic arcuate nucleus sense the energy state of an animal and regulate satiety to maintain homeostasis. Neuropeptide Y/agouti-related peptide (NPY/AgRP) neurons also participate in energy balance, but instead drive hunger. Disruptions in this circuit can promote the development of obesity, which frequently occurs during menopause due to the loss of estrogens. The primary female sex hormone, 17β-estradiol (E2) exerts an anorexigenic effect, decreasing food intake and increasing activity. These behavioral changes are mediated, in part, through inhibition of NPY/AgRP and potentiation of POMC signaling. For the first time we report that POMC neurons provide direct input to NPY/AgRP neurons primarily through glutamate and β-endorphin release. Furthermore, E2 enhances POMC neurotransmission to inhibit NPY/AgRP neurons. ER -