Anesthesia of P4, P5 or P6 rats with sevoflurane for 6 h resulted in an acute increase in serum levels of corticosterone and in exacerbated endocrine responses to stress in adulthood. A: Histograms show serum levels of corticosterone immediately after 6 h of anesthesia with sevoflurane at P4, P5 or P6 in rats of both genders. Numbers of animals per treatment group: negative control (n = 6), maternal separation (n = 6), sevoflurane (n = 6). Each group consisted of 3 male and 3 female pups. *P < 0.001 vs. all other groups. B and C: Histograms showing serum levels of corticosterone in P120 female (B) and male (C) rats 5 min after physical restraint for 30 min. Each treatment group consisted of 6 rats. Two additional groups of male rats were pretreated with either bumetanide (1.82 mg/kg, intraperitoneally) or RU28318 (10 mg/kg, intraperitoneally) 15 min prior to initiation of anesthesia with sevoflurane for 6 h at P4, P5 or P6. *P < 0.001 vs. all other groups (B), and *P < 0.001 vs. all other groups (C).#P<0.001 vs. maternal separation, &P=0.006 vs. negative control (C). @P=0.002 vs. corresponding female treatment group (B and C).