Accumulating evidence has revealed critical roles of peripheral signals, such as adipokines, in regulating appetite and energy metabolism in the hypothalamus, a brain area closely associated with homeostatic body weight regulation. Chemerin is a newly discovered adipokine and a natural ligand for the G protein coupled receptors CMKLR1 and GPR1. The chemerin/CMKLR1 axis is involved in inflammation and energy metabolism and has been hypothesised as a possible link between obesity and the development of type 2 diabetes (1). In support, local chemerin gene expression and circulating levels are elevated in humans affected by obesity. In animal studies, chemerin has been shown to modulate hypothalamic neuropeptides that control feeding and energy homeostasis (2). Here, we used a combination of in vivo and in vitro studies to examine signalling pathways activated by chemerin and how this links to the control of body weight and feeding. Using single-cell RNA sequencing, we found cell-specific expression of chemerin and CMKLR1 in mouse hypothalamic tanycytes, neurons and microglia. Using fluorescence in situ hybridization probing for chemerin followed by immunostaining for vimentin, we confirmed that chemerin mRNA is expressed by tanycytes in male Sprague Dawley rats. To show that chemerin activates hypothalamic cells, we investigated ERK and Akt signalling in vitro and in vivo. In hypothalamic neural cells, chemerin treatment (10nM) induces ERK1/2 phosphorylation peaking at 11 min (n=4/group). Akt phosphorylation occurred more quickly and peaked at 6 minutes (n=4/group). Likewise, chemerin (100nM) stimulated ERK1/2 phosphorylation within 15 min of intranasal administration in male C57BL/6 mice (n=5/group). Interestingly, chemerin treatment resulted in an increased expression of the pro-inflammatory markers IL-6 and TNFα (t-test: p=0.003, fold change vs vehicle control (FC)=2.69 and p=0.004, FC=2.96, respectively; n=4/group), thus it may play a role in acute hypothalamic inflammation. In line with our in vivo data (2), chemerin treatment (10nM) upregulated the appetite regulatory genes AgRP (FC=4.21) and NPY (FC=4.49) (t-test: p<0.05 vs vehicle control, n=4/group), suggesting that it contributes to the neuroendocrine control of appetite. To further test this, we used the small molecule CMKLR1 antagonist 2-(α-naphthoyl) ethyltrimethylammonium iodide (α-NETA) to block chemerin/CMKLR1 signalling in the hypothalamus. A single injection of 5μM α-NETA into the third ventricle of the hypothalamus of male Sprague Dawley rats significantly reduced body weight over 24 hours (t-test, p<0.05, body weight change: 3.20g±0.65 vs -6.43g±3.96; n=5/group). This was accompanied by a reduction in food intake (24.3g±0.86 vs 20.39g±2.6, n.s.). This study demonstrates the potential of the chemerin/CMKLR1 axis as a possible therapeutic target for anti-obesity treatment.