Chemogenetic activation of Calca neurons, which reside in the external lateral PBN (elPBN),12 promotes anorexia, adipsia, and escape-like behaviors,21,30 whereas more robust stimulation with optogenetics can induce freezing, bradycardia, and fear-like behaviors.28,31 Most assays have examined effects of transient activation, but chronic activation can promote severe anorexia,30 and the neurological effects of cancer cachexia have been shown to depend on activation of PBN Calca neurons.26 We show here that activation of Calca neurons is necessary to establish allodynia after nerve ligation. This evidence concerns the gene CALCA and Anorexia.