HRH3 and major depressive disorder: Noteworthy, and in two different studies that tested the effect of the H3R antagonist/inverse agonist ciproxifan on depression induced by chronic unpredicted stress, an elevation of depression-like symptoms such as anhedonia, helplessness, and social deficits was reported in numerous rodent models, including forced swim test, tail suspension test (Je et al., 2012), sucrose preference test, and social behavior test (Kumar et al., 2019), respectively.