Bed nucleus of stria terminalis enkephalin neurons contribute to depletion-induced salt appetite

The overconsumption of sodium contributes to a wide range of detrimental health conditions. Thus, it is imperative to gain a better understanding of the neural mechanisms driving sodium appetite. Here, we combined neuroanatomic, transgenic, behavioural and chemogenetic approaches to investigate the role of bed nucleus of stria terminalis (BNST) enkephalin neurons (BNST^ENK) in sodium appetite in male and female pENK-Cre mice. Our results demonstrate that Gi-mediated signalling onto BNST^ENK neurons regulates salt consumption following sodium depletion, but does not impact upon taste preference when replete. Further, Gi-mediated signalling onto BNST^ENK neurons had no effect on deprivation-induced food or water intake, or anxiety-like behavior. Using Cre-dependent retrograde trans-synaptic tracing and anterograde AAV tracing we show connectivity between BNST^ENK neurons with the extended amygdala, thalamus and hypothalamus. In summary, we have identified that BNST^ENK neurons are integral to a needs-based salt appetite and demonstrate the broader connectivity of these neurons providing a roadmap for future circuit interventions.<b>Significance Statement</b> We identify a functional role for BNST^ENK neurons in a needs-based salt appetite following sodium depletion. Further, we map the upstream and downstream connectivity of BNST^ENK neurons to provide a roadmap for future investigations into the broader circuitry underpinning salt appetite.