Fig. 2. Effects of pretreatment with intrathecal yohimbine and methysegide on antinociception of intraperitoneal ketamine 50 mg/kg. Saline, yohimbine, and methysegide were administered 10 min before ketamine injection. Data are presented as mean ± SD, n = 6. *Statistical significance between saline plus ketamine and yohimbine plus ketamine. #Statistical significance between saline plus ketamine and methysergide plus ketamine.