MEMORY FACILITATION BY POSTTRAINING EXPOSURE TO HALOTHANE, ENFLURANE,AND ISOFLURANE IN DDN MICE

The effect of low and high concentrations of halothane, enflurane, and isoflurane on posttraining memory function was studied in male ddN mi ce. Mice were trained to escape an aversive electric foot shock as an unconditioned stimulus within 3 s after being exposed to light and a b uzzer as a conditioned stimulus. Immediately after training (first ses sion: 30 trials), the animals were exposed to halothane, enflurane, or isoflurane for 120 min and then were tested again on the avoidance ta sk (second session: 30 trials) 22 h after cessation of exposure. The p erformance ratios, [B/A] (i.e., A is the score in the first session, a nd B the score in the second) were compared between the anesthetized g roups and their respective control (nonanesthetized) groups. Mean perf ormance ratios in the control groups ([B/A]c) ranged from 136.8% to 16 3.9% and those in the anesthetized groups ([B/A]a) ranged from 151.4% to 174.7%. [B/A] in each anesthetized group exceeded [B/A] in its corr esponding control group. [B/A]a significantly exceeded [B/A]c by 13.1% in the 1.23 minimum alveolar concentration (MAC) enflurane group (P < 0.05) and by 12.4% in the 0.29 MAC isoflurane group (P < 0.05). These results suggest that posttraining exposure to volatile anesthetics fa cilitates memory.