Given that both brain inflammation (Lu et al., 2017; Khodanovich et al., 2018) and GSK3β activity (Li et al., 2004; Beaulieu et al., 2008) are known to be influenced by brain 5-HT levels, the current work examined whether low 5-HT impacts the effects of HFD on GSK3β phosphorylation or the mRNA expression of several genes involved in inflammation. This evidence concerns the gene GSK3B and inflammation.