Effects of chronic lithium treatment on anxious behaviors and serotonergic genes expression in the midbrain raphe nuclei in defeated male mice

There are experimental data that mixed anxiety/depression-like state induced by chronic social defeat stress is accompanied by development of anxiety and downregulation of serotonergic gene expression in the midbrain raphe nuclei of male mice. The paper aimed to study the effect of chronic lithium chloride (LiCl) on anxious behaviors and the expression of serotonergic genes (Tph2, Slc6a4, Htr1a, Htr5b) in the midbrain raphe nuclei of defeated mice. Slight anxiolytic effects of LiCl were found on the commucativeness in the partition test, and anxiogenic-like effects, estimated by the elevated plus-maze and social interactions tests. Chronic LiCl treatment induced overexpression of the serotonergic genes in the midbrain raphe nuclei of defeated mice. We can assume that effects of LiCl, rather anxiogenic, may be due to activation of serotonergic system induced by hyperexpression of serotonergic genes. Our findings will allow to understand the factors involved in the positive and side effects of lithium on anxiety and function of serotonergic genes which are involved into mechanisms of depression.