GABA_A receptor regulation of corticosterone in PKCε-null mice. (a) Corticosterone levels measured 30 minutes after injection of saline or bicuculline in hybrid male PKCε-null (open circles; n = 3–7) and wild-type mice (filled circles; n = 4–6). Two-way ANOVA revealed an effect of genotype (F_1,25 = 16.11, P < 0.001) and concentration (F_2,25 = 7.32, P = 0.003) and a significant interaction between these factors (F_2,25 = 3.979, P = 0.032). *P < 0.05 compared with saline-treated wild-type mice and with bicuculline-treated PKCε-null mice (Tukey’s test). (b) Corticosterone levels in hybrid male PKCε-null (open circles; n = 6–12) and wild-type mice (filled circles; n = 6–10) after intraperitoneal injection of saline or allopregnanolone followed by 10 minutes of restraint. Two-way ANOVA revealed an effect of genotype (F_1,41 = 4.96, P = 0.032) and concentration (F_2,41 = 5.85, P = 0.006) and a significant interaction between these two factors (F_2,41 = 3.53, P = 0.039). *P < 0.05 compared with saline-treated PKCε-null mice and allopregnanolone-treated wild-type mice (Tukey’s test). (c) PKCε-like immunoreactivity in the PVN of wild-type (PKCε+/+) and PKCε-null (PKCε–/–) mice. Bar, 100 μm.