Figure 2.

Labetalol-infused mice learned and remembered the olfactory associative task as well as the control mice. (A) Experimental design. Two groups of mice (saline n = 7; labetalol n = 9) underwent spaced olfactory associative learning for 5 d and received intrabulbar infusion (labetalol or saline) 20 min before each training session. BrdU was injected 13 d before training. Five days after the last session of conditioning (D10), mice underwent a probe test and were killed 1 h after the last trial. (B) Labetalol-infused mice learned the task like saline-infused ones as shown by the decrease in latency to find the reward associated with (+) Limonene. (***) P < 0.001, Bonferroni post hoc test for comparison of Day 1 versus Day 5. (C) Both groups of mice showed an increase in the percentage of correct choices during the 5 d of conditioning. Five days after this training period (Probe test), labetalol- and saline-infused mice still displayed a high percentage of correct choices. (***) P < 0.001, Bonferroni post hoc tests for comparison of Day 1 versus Day 5 and Day 1 versus Probe test. (n.s.) nonsignificant (P > 0.05), Bonferroni post hoc test for comparison of Day 5 versus Probe test. Outlier trials that deviated from the mean by more than two SEM were excluded from analysis (one mouse out of 17). (D) Labetalol-infused mice, like control mice, visited the odorized hole ((+) Limonene) significantly more than the one without odorant. (E) Labetalol- and saline-infused mice spent significantly more time investigating the odorized hole. (*) P < 0.05, (**) P < 0.01, (***) P < 0.001, Bonferroni post hoc tests for comparison of (+) Limonene versus nonodorized hole. (F) Labetalol infusions did not affect newborn cell survival during olfactory associative learning, as assessed by the density of BrdU⁺ cells in the granule cell layer of conditioned mice (23 d post-BrdU injection; n = 3 mice for saline, n = 4 mice for labetalol, P > 0.05, bilateral unpaired t-test). All data are presented as mean ± SEM.