In this article, we present our data on the upregulation of serotonergic genes Tph2, Slc6a4, Htr1a, and Htr5b in the midbrain raphe nuclei after preventive LiCl treatment; supposedly, these changes may lead to the activation of the serotonergic system and, as a consequence, to the development of anxiety as a side effect of LiCl. The gene discussed is TPH2; the disease is Anxiety.