FIGURE 5.
Altered memory extinction in the absence of PC4 in the brain. a, scheme depicting the Morris water maze experiment. b, the two mice strains (n = 9/group) were trained using a Morris water maze for 4 days. Latencies to reach the platform are represented in seconds. Acquisition in the Morris water maze was comparable between PC4+/+ Nestin-Cre and PC4f/f Nestin-Cre mice, with both strains learning significantly during the 4 days (days effect: F(3,48) = 10.273, p < 0.001; genotype effect: F(1,16) = 0.341, p = 0.56). c, Morris water maze probe trials show that memory retention was comparable between PC4+/+ Nestin-Cre and PC4f/f Nestin-Cre mice 24 h after the 3rd day of acquisition in an intermediate probe trial (iPT) and 6 days after a supplemental 4th day of acquisition (PT). The time spent in the target quadrant (Target) is represented and compared with the average time spent in the three other quadrants (Others). The chance level (15 s in one of the four quadrants in a span of 1 min) is represented by a dashed line. The time spent in the target quadrant was significantly longer than 15 s (intermediate PT, p < 0.01; PT, p < 0.001) and longer than the time spent in the other quadrants (p < 0.001). d, extinction tests were performed at 2-h intervals after the PT. Whereas the PC4+/+ Nestin-Cre mice showed a decrease in the time spent in the target quadrant, no decrease was observed in the PC4f/f Nestin-Cre mice. A significant difference between PC4+/+ Nestin-Cre and PC4f/f Nestin-Cre mice was observed for extinction trial 2 (#, p < 0.05) and extinction trial 3 (#, p < 0.01). For PC4f/f Nestin-Cre mice, all extinction values were significantly greater than 15 s (*, p < 0.05; **, p < 0.01).