Experimental protocol and time course. All rats were exposed to preoperative environmental enrichment (PEE) or sedentary condition for 14 days following surgery (laparotomy and small intestinal manipulation) or nonsurgery and allowed 7 days of recovery. Experiment 1: Cognitive testing followed by quantification of hippocampal cytokines 7 days after surgery. Experiment 2: Ex vivo measurement of proinflammatory cytokine production from primary microglia isolated from the hippocampus before intervention (baseline), after intervention, and 7 days after surgery. All of these experimental protocols were first carried out in aged rats, followed by young rats.