In an individual cage in the absence of a running wheel, marbles or any other forms of enrichment. All other factors including diet, bedding, access to water and lightdark cycle were identical. All experiments were approved by the Animal Care Committee at McGill University, and conformed to the ethical guidelines of the Canadian Council on Animal Care and the guidelines of the Committee for Research and Ethical Issues of the International Association for the Study of Pain published in PAIN, 16 (1983) 109?10. All surgery was performed under isoflurane anesthesia, and all efforts were made to minimize suffering.Environmental ManipulationThree months after injury or sham surgery, the presence of LED-209 chemical information neuropathic pain was confirmed and mice 
were randomly assigned to one of four groups: injured with enriched environment, injured with impoverished environment, sham with enriched environment, sham with impoverished environment. The standard, enriched and impoverished environments are described above. Mice were then re-tested 2 months following environmental manipulation and tissue was collected.Tissue ExtractionIn the first study (Figures 1 and 2), animals were sacrificed 6 months after nerve injury or sham surgery by decapitation following isoflurane anesthesia. In the enrichment experiment (Figures 3 and 4), animals were sacrificed 5 months after nerve injury or sham, of which the final 2 months were spent in enriched or impoverished environments. Anatomical regions were defined according to the stereotaxic coordinates (rostral audal, medial?lateral and dorsal entral from bregma) by Paxinos and Franklin [18]. The prefrontal cortex (right and left; +1 to +3, 21 to +1, 0 to 22.5), amygdala (right and left; 21 to 23, 64 to 61.5, 24 to 26), thalamus (0 to 23, 22 to + 2, 18055761 22.5 to 24.25), and visualInduction of Nerve InjuryNeuropathy was induced using the spared nerve injury model. Under deep anesthesia, an incision was made on the lateral surface of the thigh through the muscle, exposing the three terminal branches of the sciatic nerve: the sural, common peroneal 
and tibial nerves. The common peroneal and the tibial nerves wereChanges in DNA Methylation following Nerve InjuryFigure 1. Behavioral Signs of Neuropathic Pain Six Months following Nerve Injury. Nerve injured mice show a decrease in mechanical thresholds (A) and an increase in acetone-evoked behaviors, indicative of cold sensitivity (B) on the hindpaw, measured by the von Frey filament test and the acetone tests, respectively. In addition, these mice show signs of motor dysfunction, measured by the rotarod assay (C). In the open field assay (D), neuropathic mice do not differ from control mice in overall levels of spontaneous activity, measured by the number of peripheral squares covered in the open field (e). However, they spent less time spent in the central square of the open field, indicative of anxiety-like behavior (f). * = p,0.05, *** = p,0.0001, n = 10/group, error bars indicate S.E.M. doi:10.1371/journal.pone.0055259.gcortex (right and left; 22 to 24, 23 to +3, 0 to 2) were extracted, frozen on dry ice and stored at 280 C until use.DNA ExtractionTissue was homogenized and incubated in DNA extraction buffer (500 ml) CI-1011 site containing proteinase K (20 ml; 20 mg/ml; Roche, Basel, Switzerland) at 50uC for 12 h. Samples were treated with RNAase A (50 U/mg; 30 min; Roche) and phenol: chloroform (1:1) added. After phase separation, ethanol (95 ) was added to precipitate the DNA. The DNA pellet was.In an individual cage in the absence of a running wheel, marbles or any other forms of enrichment. All other factors including diet, bedding, access to water and lightdark cycle were identical. All experiments were approved by the Animal Care Committee at McGill University, and conformed to the ethical guidelines of the Canadian Council on Animal Care and the guidelines of the Committee for Research and Ethical Issues of the International Association for the Study of Pain published in PAIN, 16 (1983) 109?10. All surgery was performed under isoflurane anesthesia, and all efforts were made to minimize suffering.Environmental ManipulationThree months after injury or sham surgery, the presence of neuropathic pain was confirmed and mice were randomly assigned to one of four groups: injured with enriched environment, injured with impoverished environment, sham with enriched environment, sham with impoverished environment. The standard, enriched and impoverished environments are described above. Mice were then re-tested 2 months following environmental manipulation and tissue was collected.Tissue ExtractionIn the first study (Figures 1 and 2), animals were sacrificed 6 months after nerve injury or sham surgery by decapitation following isoflurane anesthesia. In the enrichment experiment (Figures 3 and 4), animals were sacrificed 5 months after nerve injury or sham, of which the final 2 months were spent in enriched or impoverished environments. Anatomical regions were defined according to the stereotaxic coordinates (rostral audal, medial?lateral and dorsal entral from bregma) by Paxinos and Franklin [18]. The prefrontal cortex (right and left; +1 to +3, 21 to +1, 0 to 22.5), amygdala (right and left; 21 to 23, 64 to 61.5, 24 to 26), thalamus (0 to 23, 22 to + 2, 18055761 22.5 to 24.25), and visualInduction of Nerve InjuryNeuropathy was induced using the spared nerve injury model. Under deep anesthesia, an incision was made on the lateral surface of the thigh through the muscle, exposing the three terminal branches of the sciatic nerve: the sural, common peroneal and tibial nerves. The common peroneal and the tibial nerves wereChanges in DNA Methylation following Nerve InjuryFigure 1. Behavioral Signs of Neuropathic Pain Six Months following Nerve Injury. Nerve injured mice show a decrease in mechanical thresholds (A) and an increase in acetone-evoked behaviors, indicative of cold sensitivity (B) on the hindpaw, measured by the von Frey filament test and the acetone tests, respectively. In addition, these mice show signs of motor dysfunction, measured by the rotarod assay (C). In the open field assay (D), neuropathic mice do not differ from control mice in overall levels of spontaneous activity, measured by the number of peripheral squares covered in the open field (e). However, they spent less time spent in the central square of the open field, indicative of anxiety-like behavior (f). * = p,0.05, *** = p,0.0001, n = 10/group, error bars indicate S.E.M. doi:10.1371/journal.pone.0055259.gcortex (right and left; 22 to 24, 23 to +3, 0 to 2) were extracted, frozen on dry ice and stored at 280 C until use.DNA ExtractionTissue was homogenized and incubated in DNA extraction buffer (500 ml) containing proteinase K (20 ml; 20 mg/ml; Roche, Basel, Switzerland) at 50uC for 12 h. Samples were treated with RNAase A (50 U/mg; 30 min; Roche) and phenol: chloroform (1:1) added. After phase separation, ethanol (95 ) was added to precipitate the DNA. The DNA pellet was.