Figure 1.

High doses of ketamine do not elicit antidepressant-relevant behavioral actions in mice. Mice received an injection of vehicle or different doses of racemic ketamine and were assessed for antidepressant-like responses 24 h later. A, Ketamine at the dose of 10 mg/kg significantly decreased escape failures in helpless mice, whereas the doses of 1, 3, 30, and 100 mg/kg did not exert significant antidepressant-relevant reductions in escape failures in the learned helplessness paradigm. B, Similarly, ketamine at the dose of 10 mg/kg reversed the decrease in sucrose preference of mice that underwent chronic social defeat stress whereas the high dose of 100 mg/kg did not elicit such an antidepressant-related response. Mice were tested for sucrose versus water preference during the 24-h period following drug administration. Data are the mean ± SEM; *p < 0.05, ***p < 0.001 as indicated by Holm–Šídák post hoc comparisons. See Table 1 for complete details on the statistical analyses and precise group sizes. CSDS, chronic social defeat stress; KET, racemic ketamine; SAL, saline; Treat, treatment.