Morphine treatment increases inflammatory signaling after laparotomy. Rats received laparotomy, followed by vehicle or morphine treatment on days 0–7 after surgery (5 mg/kg twice a day). Two weeks after surgery, L1/2 dorsal spinal cords were collected and mRNA expression was quantified via real-time reverse transcription-polymerase chain reaction. Expression of genes was compared between saline and morphine treatment for (A) toll-like receptor 4 (TLR4), (B) P2X7R, (C) major histocompatibility complex (MHC) class II, (D) IκBα, (E) NLRP3, (F) microRNA (miR)-223, (G) caspase-1, (H) interleukin (IL)-1β, (I) tumor necrosis factor (TNF), (J) heat shock protein (HSP-90), (K) biglycan, and (L) high mobility group box 1 (HMGB1). Data are presented as mean ± standard error of the mean; n = 6/group; *P < .05, **P < .01, ***P < .001.