Evaluation of the anxiolytic properties of Tetrahydropalmatine, a Corydalis yanhusuo compound, in the male Sprague-Dawley rat

The purpose of this study was to investigate the anxiolytic effects of tetrahydropalmatine (THP) and its potential interaction with the benzodiazepine binding site on the γ-aminobutyric acid (GABA _A) receptor in the male Sprague-Dawley rat. Tetrahydropalmatine (THP), an active component isolated from the Chinese herbal plant Corydalis yanhusuo, is used in Asia for its analgesic, sedative, and hypnotic properties during herbal therapy. Fifty-five rats were assigned to 1 of 5 groups with 11 rats per group: 1) control (vehicle), 2) THP, 3) midazolam, 4) midazolam with THP, and 5) flumazenil with THP. In this study, the elevated plus-maze measured the behavioral components of anxiety and motor movements. The data were analyzed using a 2-tailed multivariate analysis of variance to determine if a significant difference existed followed by the least significant difference post hoc test. The findings suggest that THP, 25 mg/kg, given via intraperitoneal injection, results in significant anxiolysis and decreased motor movements. Furthermore, flumazenil, 3 mg/kg, does not fully antagonize the effects of THP.