Effect of intraperitoneal administration of saline (A, B) and LPS (B) (100 μg/kg body weight) on free corticosterone in long-term intracerebroventricularly CRH-infused rats (Protocol B). A, Direct comparison of the intraperitoneally saline-treated rats from B. Basal corticosterone levels (A): ○, intracerebroventricular vehicle/intraperitoneal saline; □, intracerebroventricular CRH/intraperitoneal saline. Effect of intraperitoneal injection of LPS (B): •, intracerebroventricular vehicle/intraperitoneal LPS; ▪, intracerebroventricular CRH/intraperitoneal LPS. Saline or LPS was injected at 11:30 A.M. on day 7 of the infusion treatment, as indicated by thearrow. Dialysate corticosterone (μg/dl) was measured from 9 A.M. to 5:30 P.M. For more details see Materials and Methods. The time points on the x-axis correspond to the time of the day at which collection of the 30 min sample was started. Values represent mean ± SEM (n = 6–7). *, First time point of significance for intracerebroventricular vehicle/intraperitoneal LPS compared with intracerebroventricular vehicle/intraperitoneal saline; +, first time point of significance for intracerebroventricular CRH/intraperitoneal LPS compared with intracerebroventricular CRH/intraperitoneal saline (Student’st test). For additional statistical analyses, see Results.