Stress hormone responses. (a) Mean ± SEM corticosterone levels in hybrid male mice before restraint (basal; n = 23 wild-type, 22 PKCε-null), after 10 minutes of restraint (n = 11 of each genotype), or 1 hour after restraint (n = 6 of each genotype). Two-factor ANOVA showed significant effects of genotype (F_1,73 = 24.03; P < 0.001) and treatment (F_2,73 = 33.44; P < 0.001). *P < 0.05 compared with wild-type levels for each treatment and †P < 0.05 compared with basal levels in same genotype (Tukey’s test). (b) Basal ACTH levels were elevated in hybrid male wild-type mice (n = 16) compared with PKCε-null (n = 13) mice (P = 0.012, two-tailed t test). (c) Corticosterone levels in hybrid male mice 30 minutes after intraperitoneal injection (500 μl) of saline, 10 μg/kg CRF, or 100 mg/kg metyrapone. Two-factor ANOVA showed a significant effect of treatment (F_2,76 = 18.5, P < 0.001) but not genotype, with levels higher after CRF and lower after metyrapone than after saline (P < 0.001, Newman Keuls test). *P = 0.026 compared with saline-treated wild-type mice (Newman Keuls test). (d) ACTH levels in hybrid male mice 30 minutes after treatment with saline, CRF, or metyrapone. Two-factor ANOVA revealed an effect of treatment (F_2,62 = 9.81, P < 0.001) but not of genotype with ACTH levels higher after CRF or metyrapone than after saline (P < 0.05, Newman Keuls test).