Heterogenous thirst sensitive neurons within the anterior cingulate cortex modulate water intake in response to dehydration in mice

Abstract

The anterior cingulate cortex (ACC) has recently emerged as a cortical structure involved in body fluid homeostasis. Human fMRI studies indicate that the activity of the ACC is augmented with dehydration, but the ingestion of fluid abrogates this effect. Extracellular dehydration increases the synthesis of angiotensin II, which acts on receptors in the brain to mediate fluid ingestion. Here, we test the hypothesis that neurons in the ACC that express the angiotensin type-2 receptor (AT2R) are mediators of thirst and fluid consumption. We found an abundance of neurons within the ACC that expressed AT2R (referred to as ACCAT2R). To determine whether ACCAT2R couple their activity to dehydration and fluid consumption, we delivered Cre-inducible adeno-associated virus synthesizing the calcium indicator, GCaMP6f, into the ACC of male AT2R-Cre mice. Following implantation of a GRIN lens targeting the ACC, we used a head-mounted miniscope to record calcium events in conscious freely moving mice under conditions of euhydration, dehydration and rehydration. Dehydration significantly excited a subset of ACCAT2R but these neurons became inhibited as mice initiated rehydration with water ingestion. Interestingly, we also discovered a different subset of ACCAT2R neurons that coupled their excitation to the consumption of water during rehydration. To evaluate the function of ACCAT2R, we used Cre-inducible adeno-associated virus to direct the expression of excitatory (ChR2) or inhibitory (SwiChRca) opsins to the ACCAT2R. In vivo optogenetic experiments revealed that excitation or inhibition of ACCAT2R attenuated dehydration-induced water intake, suggesting that ACCAT2R may be comprise of a heterogenous population of neurons. Indeed, RNAscope in situ hybridization found that ACCAT2R neurons were either GABAergic or glutamatergic. Follow-up anatomical and electrophysiological studies confirmed that GABAergic ACCAT2R made local inhibitory synapses onto neighboring neurons whereas glutamatergic ACCAT2R sent long-range projections to the zona incerta (ZI). Next, we utilized intersectional genetics to selectively target GABAergic ACCAT2R and found that optogenetically exciting this subset of neurons attenuated dehydration-induced water intake. Ongoing experiments investigate whether the activity of glutamatergic ACCAT2R that project to the ZI is coupled to fluid consumption. Collectively, our studies suggest that subsets of ACCAT2R may differentially contribute to the sensation of thirst and fluid consumption, possibly by altering the perception of hydration state. This work was supported by American Heart Association grant 17GRNT33660969 and National Institute of Health (National Heart Lung and Blood Institute) grants HL-125805 (ADdK), HL-145028 (ADdK), HL-136595 (EGK), HL-096830 (EGK) HL-122494 (EGK). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.