Anxiolytic activity of endogenous nootropic dipeptide cycloprolylglycine in elevated plus-maze test.

Testing in an elevated plus-maze revealed dose-dependent anxiolytic activity of piracetam analog cycloprolylglycine. Intraperitoneal injection of this agent (0.05 mg/kg) 9-fold prolonged the time spent in open arms compared to the control, without affecting the total motor activity. This effect was stereo-selective: D-enantiomer in doses of 0.05 and 0.1 mg/kg was inactive. Therefore, cycloprolylglycine is similar to piracetam in not only nootropic, but also anxiolytic activity. The existence of an endogenous system responsible for the co-regulation of memory and anxiety is hypothesized.