Exercise Reduces Effects of 5-HT2CR Agonist Intra-DS cannula placements are shown in Figure 4A. After exclusion of rats with misplaced cannulae, group sizes were Sedentary/0.3 mM = 7; Sedentary/2.0 mM = 12; Sedentary/ 6.0 mM = 11; Run/0.3 mM = 9; Run/2.0 mM = 15; Run/ 6.0 mM = 9. Data from rats with misplaced cannulae (Seden- tary/2.0 mM = 2; Sedentary/6.0 mM = 1; Run/6.0 mM = 3) were averaged and included as off-site controls. Saline was not injected into the DS in this study because our results from the above amygdala study, as well as our prior studies [50], indicate that saline injected animals behave identically to animals injected with 0.3 mM CP-809101. The effect of the 5-HT2CR agonist CP809101 on freezing blocks and average freezing behavior are shown in Figure 4B and Figure 3C, respectively. Pre-shock freezing was minimal and did not differ between groups (Figure 4B, pre-FR-1). While there was an expected effect of time (F (9, 513) = 36.546; p,0.0001) on freezing behavior during freezing blocks, neither physical activity status nor intra-DS administration of CP-809101 prior to behavioral testing impacted freezing behavior. ANOVA revealed a significant main effect of exercise on FR-1 behavior (p = 0.003), i.e. exercise groups had faster average FR-1 escape latencies than sedentary groups. However, neither the main effect of drug nor the interaction between exercise and drug were significant (Figure 4D, FR-1). Repeated measures ANOVA revealed significant main effects of time (F (4, 228) = 16.919; p = ,0.0001) and drug (F (2, 57) = 3.476; p = 0.0376), as well as reliable time6drug (F (4, 228) = 2.384; p = 0.0174) and time6 drug6exercise (F (8, 228) = 3.232; p = 0.0017) interactions on FR- 2 escape blocks (Figure 4D). Average FR-2 escape times are shown in Figure 4E. Post hoc analysis revealed that there was no Figure 4. Six weeks of voluntary wheel running reduces the deficit in instrumental escape learning produced by 5-HT2C receptor activation in the dorsal striatum. Fifteen minutes prior to behavioral testing, sedentary and physically active (Run) rats received intra-DS microinjections of the 5-HT2C receptor agonist CP-809101 (0.3 mM, 2.0 mM or 6.0 mM). (A) Cannula tip placement within the DS. Sedentary rats are denoted with black triangles, physically active rats are denoted with gray triangles, and off-site placements are denoted with an X. Brain illustrations adapted from Paxinos and Watson (published in the Rat Brain in Stereotaxic Coordinates, 4th ed., Copyright Elsevier (1998)). Numbers left of illustrations refer to distance from Bregma (mm). (B) Freezing behavior over the duration of the post-FR-1 freezing observation period presented in 2 minute blocks (pre-shock scores are not different and therefore overlap). (C) The mean percent time spent freezing during the 20 minute observation period. (D) Shuttle box escape latencies for one block of 2 FR-1 trials (FR-1) and five blocks of 5 FR-2 trials (FR-2). (E) The mean escape latency for all 25 FR-2 escape trials. Data represent group means 6 SEM. * p,0.05 relative to 0.3 mM groups and off-site control group; W p,0.05 relative to 2.0 mM sedentary group. doi:10.1371/journal.pone.0046118.g004 PLOS ONE | www.plosone.org 6 September 2012 | Volume 7 | Issue 9 | e46118