Exercise Reduces Effects of 5-HT2CR Agonist pixels above background). Each subject’s mean integrated density at a given level represents the average of at least 2 slices chosen for analysis between the following coordinates: Striatum from +1.60 to +0.20 mm anterior to bregma; amygdala and lateral ventricle from 22.56 to 23.30 mm posterior to bregma based on the atlas by Paxinos and Watson [58]. Templates for each region were made to ensure that equivalent areas were analyzed between animals. Lateral ventricle was analyzed as a control region because the choroid plexus of the lateral ventricle expresses relatively large amounts of 5-HT2CR mRNA. Statistical Analysis Body weights were analyzed with repeated measures ANOVA. Pre-shock freezing scores were averaged into 1 pre-shock score and analyzed with ANOVA. Shock-elicited freezing scores were Figure 2. Six weeks of voluntary wheel running reduces the increase in fear behavior produced by 5-HT2C receptor activation in the region of the lateral/basolateral amygdala (BLA). Following 6 weeks of voluntary wheel running (Run) or no running (Sedentary), rats received intra-BLA microinjections of either saline or the selective 5-HT2C receptor agonist CP-809101 (0.3 mM, 2.0 mM, or 6.0 mM). Shockelicited freezing and shuttle box escape latency were measured sequentially in shuttle boxes 15 minutes later. (A) Cannula placement within the amygdala. Sedenatry 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) Mean freezing behavior presented in 2 minute blocks (pre-FR-1 scores are not different and therefore overlap). Error bars are ommited for clarity. (C) The mean percent shock-elicited freezing for the entire 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). Error bars are omitted for clarity. (E) The mean escape latency for all 25 FR-2 escape trials. Data represent group means 6 SEM. * p,0.05 relative to Offsite Control, Sedentary/Saline, Sedentary/ 0.3 mM, Run/2.0 mM, and Run/6.0 mM groups. W p,0.05 relative to the Sedentary/2.0 mM group. h p,0.05 relative to the Run/2.0 mM group. doi:10.1371/journal.pone.0046118.g002 PLOS ONE | www.plosone.org 4 September 2012 | Volume 7 | Issue 9 | e46118