Escherichia coli endotoxin 0111 b4

In the present study, the rats were injected with either LPS (Escherichia coli endotoxin 0111: B4, Sigma, Lot # 064M4125V, Shanghai, China; 1 mg/kg LPS, a single-dose, intraperitoneal injection) or equal-volume (0.9%) normal saline (a single-dose, intraperitoneal injection). To maintain circadian effects, all the injections were completed between 8:00 and 9:00 a.m. The dose of LPS was designed as neurobehavioral-abnormality-causing, but not lethal [22 (link)–24 (link)].

We established the animal models of sepsis by utilizing LPS in a rodent model of sepsis as previously described [5 (link), 6 (link)]. For LPS injection, mice received LPS (Escherichia coli endotoxin 0111: B4, Lot # 064M4125V, Sigma, Shanghai, China, 5 mg/kg). All the procedures were performed by an experienced investigator to keep the model stable.
CLP model was induced as we previously described [4 (link)]. Briefly, animals were anesthetized with 2% sodium pentobarbital (50 mg/kg; Sigma Chemical Co, St. Louis, MO, USA) by intraperitoneal (i.p.) injection and a 1-cm ventral midline laparotomy was performed. After then, the cecum was carefully exposed and ligated with a 4.0 silk suture, about 0.5 cm below the ileocecal valve. Subsequently, the cecum was perforated with 22–gauge needle and gently compressed to extrude a small amount of feces. Finally, the cecum was returned to the peritoneal cavity and the laparotomy was closed with 4.0 silk sutures. Immediately after the operation, animals received fluid resuscitation with normal saline solution (subcutaneously, 20 ml/kg of body weight) and antibiotic therapy (ertapenem, 20 mg kg^-1; Merck Research Laboratory, USA). All mice were returned to their cages with free access to food and water. For sham group, animals were treated identically without ligation or puncture of the cecum.

We developed a mouse model of SAE by LPS administration, which have been well described in previous studies [4 (link), 5 (link)]. Animals were injected intraperitoneally (i.p.) with either LPS (5 mg/kg) (Escherichia coli endotoxin 0111: B4, Sigma, Lot # 064M4125V) or equal volume (0.9%) normal saline (NS). Our preliminary data showed that this dose and route of administration resulted in a hippocampal-dependent cognitive impairment.