A) Mean (± SEM) plasma corticosterone concentrations are significantly (bars with differing letters above, such as A vs B) elevated by aggressive social interactions, in both Escape (light gray bar) and Stay (dark gray bar) phenotype mice compared to home-cage controls (white bar). B) Among Escape mice, icv injection with an Orx2 antagonist 2 days prior (on day 3, light gray left hatched bar) does not affect plasma corticosterone on test (5) day. In contrast, among Stay phenotypes, icv injection on day 3 with an Orx2 antagonist (dark gray, left hatched bar) stimulates increased plasma corticosterone measured on day 5 compared to vehicle treated Stay mice (§), antagonist treated Escape mice (‡), and C) Orx2 agonist (dark gray, right hatched bar) Stay mice.