Reciprocal Control of Drinking Behavior by Median Preoptic Neurons in Mice.

Neurons in the median preoptic nucleus (MnPO) and organum vasculosum of the lamina terminalis (OVLT) are known to regulate fluid/electrolyte homeostasis, but few studies have examined this issue with an appreciation for the neurochemical heterogeneity of these nuclei. Using Cre-Lox genetic targeting of Channelrhodospin-2 in transgenic mice, we demonstrate that glutamate and GABA neurons in the MnPO/OVLT reciprocally regulate water consumption. Stimulating glutamatergic MnPO/OVLT neurons induced water consumption, whereas stimulating GABAergic MnPO neurons caused a sustained and specific reduction in water consumption in dehydrated mice, the latter highlighting a heretofore unappreciated role of GABAergic MnPO neurons in thirst regulation. These observations represent an important advance in our understanding of the neural circuits involved in the regulation of fluid/electrolyte homeostasis.