Figure 4.

(A) The performance of 4-month-old mutant mice (n = 20) in the water maze is unchanged to that of 10-month-old matched wild-type controls. An ANOVA on the mean latencies to escape with factors of genotype and blocks revealed no significant main effect of genotype at 4 months of age. (B) During the probe trial in which the platform was removed and the mice swam freely for 60 s, there were no significant differences between the 4-month-old galanin mutant mice and the age-matched wild-type control mice in the speed at which they swam in the maze, the time they spent in the northeast quadrant, the number of times they crossed the exact position of the platform, and the distance they swam in the northeast quadrant. At this age, both groups spent over 33% of their time during the probe trial in the northeast quadrant, indicating both had encoded the position of the platform relative to the spatial cues provided. (C) In contrast, at 10 months of age, the performance of the wild-type control mice (n = 20) was significantly better from day 15 onward (P < 0.05) than that of the galanin mutant mice. (D) The behavior of the 10-month-old galanin mutant mice was also significantly worse in the probe trial than that of the wild-type controls, in that they spent significantly less time in the northeast quadrant (P < 0.05, F = 9.04), swam a shorter distance in the northeast quadrant (P < 0.05, F = 9.30), and made significantly fewer crossings of the exact location of the platform at this age (P < 0.05, F = 4.98). These differences could not be accounted for by the speed at which they swam, as this did not significantly differ from that of the wild-type controls, suggesting an impairment in learning or memory.