Utility of an elevated plus-maze for the evaluation of memory in mice: effects of nootropics, scopolamine and electroconvulsive shock

An elevated plus-maze consisting of two open and two enclosed arms was employed for an evaluation of memory in mice. Mice in the plus-maze escaped from the open arm to the enclosed arm because mice apparently dislike open and high spaces. The time it took for the mice to move from the open arm to the enclosed arm (transfer latency) was recorded. The transfer latency after the 2nd day was significantly shorter than that on the 1st day when it was recorded at a rate of one trial a day for 5 days. The transfer latency on the 2nd day was significantly prolonged in the mice administered electroconvulsive shock (300 V, 1 s) or scopolamine (20 μg, ICV) immediately after the first trial compared to the transfer latency in the control group. The prolongation of transfer latency in the mice administered an electroconvulsive shock was reversed by pretreatment with aniracetam (20 mg/kg, PO), but not tacrine and physostigmine. The prolongation of transfer latency in the mice administered scopolamine was reversed by pretreatment with aniracetam (10 and 20 mg/kg, PO) tacrine (1 and 3 mg/kg, PO), or physostigmine (0.025-0.2 mg/kg, IP). These results suggest that transfer latency may be one of the parameters of learning and memory.