Neuromedin U Neurons in the Edinger–Westphal Nucleus Respond to Alcohol Without Interfering with the Urocortin 1 Response

The Edinger–Westphal nucleus (EW) is a midbrain nucleus composed of a preganglionic, cholinergic subpopulation and a densely clustered peptidergic subpopulation (EWcp). The EWcp is one of the few brain regions that show consistent induction of FOS following voluntary alcohol intake. Previous results in rodents point to urocortin 1 (UCN1) as one of the peptides most involved in the control of ethanol intake and preference. Notably, the functions described for UCN1, such as reward processing, stress coping or the regulation of feeding behavior are similar to those described for the neuropeptide neuromedin U (NMU). Interestingly, NMU has been recently associated with the modulation of alcohol-related behaviors. However, little is known about the expression and functionality of NMU neurons in alcohol-responsive areas. In this study, we used the recently developed Nmu-Cre knock-in mouse model to examine the expression of NMU in the subaqueductal paramedian zone comprising the EWcp. We delved into the characterization and co-expression of NMU with other markers already described in the EWcp. Moreover, using FOS as a marker of neuronal activity, we tested whether NMU neurons were sensitive to acute alcohol administration. Overall, we provided novel insights on NMU expression and functionality in the EW region. We showed the presence of NMU within a subpopulation of UCN1 neurons in the EWcp and demonstrated that this partial co-expression does not interfere with the responsivity of UCN1-containing cells to alcohol. Moreover, we proposed that the UCN1 content in these neurons may be influenced by sex.