Abstract: Objective To observe the effects of ketamine administered repeatedly on the ability of learning and memory as well as the expression of TSPO protein in hippocampus in juvenile mice. Methods A total of 24 juvenile Wistar mice, aged 21 days, were randomly divided into the control group (n=12), which received intraperitoneal injection of NS, and the ketamine group (n=12), which received intraperitoneal injection of ketamine,1 time a day for 7 consecutive days. To observe the learning and memory function of mice, Morris water maze was performed in both groups, including 4-day trail and 1-day probe. After behavior test, the morphological changes and number of the microglia cells and the level of TSPO protein in the bilateral hippocampus tissues were observed using double immunofluorescence standard technique and Western blotting. Results From trail day 3-4, latencies of mice in the ketamine group were significantly longer than those in the control group (P <0.01). On the probe day, time and frequency during platform quadrant in the ketamine group were significantly shorter than those in the control group (P <0.01). In hippocampus area, Western blotting showed that microglia and TSPO proteins increased; immunofluorescence showed morphological changes in the microglia and higher expression of TSPO protein in the ketamine group. Conclusion Ketamine anesthesia reduces not only learning ability but also spatial memory in mice. The microglia cells of hippocampus are activated and TSPO protein is increased.

Key words: Ketamine, Microglia cell, Learning and memory ability, 18 kDa translocator protein