Motor function in an animal model with ouabain-induced bipolar disorder and comorbid anxiety behavior

In a clinical setting, anxiety disorder is highly correlated with bipolar I disorder in humans. However, the comorbidity of anxiety behavior and bipolar disorder still remains unclear in an animal model. This study utilized an ouabain-induced animal mode to examine anxiety and mania in an open field test. In the present study, 5 µl of artificial cerebrospinal fluid (aCSF) or ouabain (10^-5, 10^-4, and 10^-3 M) were administered into the left ventricle. The animals' motor functions and anxiety behaviors were measured for 15 min. The results showed that 10^-3 M ouabain significantly increased the animal's total distance traveled, average speed, and maximum speed compared to the control group. The time spent inside (i.e., how much time rats spent in the center of the square) and the inside-outside times of the central square (i.e., how many times rats ran across the center square) of the higher-concentration groups (10^-4 M and 10^-3 M) were significantly decreased. Therefore, a high concentration of ouabain may induce hyperactivity. The 10^-4 M and 10^-3 M ouabain groups exhibited more anxiety behaviors. The study is the first model to examine comorbid anxiety behaviors and bipolar disorder in an animal model. The study provides some insights for comorbid anxiety and bipolar disorder in clinics.