NTSHSD2 neuron activity: regulation by aldosterone and afferent control” - PROJECT SUMMARY/ABSTRACT NTSHSD2 neurons are activated by aldosterone and detect sodium deficiency. When activated, NTSHSD2 neurons drive robust sodium appetite, while their ablation reduces intake. As key regulators of sodium appetite, how NTSHSD2 neuron activity is controlled is of great interest. During sodium deficiency or mineralocorticoid excess, NTSHSD2 neurons exhibit increased spontaneous activity in ex vivo brain slice recordings, which we hypothesize is mediated by aldosterone-mineralocorticoid receptor (MR) signaling. However, the molecular mechanisms through which aldosterone-MR signaling acts to drive NTSHSD2 neuron activity are unknown. Further, sodium ingestion has been shown to rapidly decrease Fos expression by NTSHSD2 neurons, indicating active inhibition of NTSHSD2 neurons. Such rapid control is likely to be mediated by neural input, but the specific afferent neurons that regulate NTSHSD2 neuron activity are yet to be elucidated. The goal of this grant is to study mechanisms by which NTSHSD2 neuron activity is controlled. Aim 1 will determine how aldosterone-MR signaling regulates NTSHSD2 neuron activity. We propose a key role for genomic regulation by aldosterone-MR signaling for driving intrinsic activity of NTSHSD2 neurons during sodium deficiency and mineralocorticoid excess. Aims 2 and 3 will define the wiring diagram of inputs to NTSHSD2 neurons as these very afferents are also likely sensitive to alterations in extracellular fluid volume and/or sodium intake. This will be accomplished through single cell transcriptional profiling of NTS afferent neurons to identify their marker genes, which will then be leveraged to gain access to the afferent neurons using Cre driver mice. Connectivity to NTSHSD2 neurons will then be established by performing channelrhodopsin-2 (ChR2)-assisted circuit mapping (CRACM). Finally, we will also specifically investigate regulation of NTSHSD2 neurons by the central amygdala (CeA) – a GABAergic structure linked to appetite control with neurons that provide input to NTSHSD2 neurons. Our goal is to identify the information carried by these afferents and their effects on sodium appetite. The experiments proposed in this project will address significant gaps in our knowledge regarding the regulation of NTSHSD2 neurons by providing both molecular and circuit mechanisms for the control of their activity.
