Spatial memory performance 2 weeks after general anesthesia in adult rats.

We have previously demonstrated that general anesthesia with 1.2% isoflurane-70% nitrous oxide impairs acquisition of a radial arm maze task in both young and aged rats when testing begins 2 days after anesthesia and in aged rats when testing begins 2 wk later. We designed this study to examine whether postanesthesia learning impairment is persistent in young rats. Six-month-old rats were randomized to anesthesia for 2 h with 1.2% isoflurane-70% nitrous oxide, 1.8% isoflurane, or a control group that received 30% oxygen (n = 10 per group). Rats recovered for 2 wk and were then tested daily on a radial arm maze for 14 days. There were no differences between the controls and anesthesia groups in number of correct choices to first error or time to complete the maze. There was no main effect of group in terms of total number of errors (P > 0.05) but the group by day interaction was significant (P < 0.05), reflecting improved performance in the 1.2% isoflurane-70% nitrous oxide group relative to controls during the later days of testing (P < 0.005). Hence, in adult rats, previous general anesthesia is not associated with impaired learning 2 wk later. In fact, previous 1.2% isoflurane-70% nitrous oxide improves maze performance 2 wk later.