Experiment 1: Male C57BL/6N mice were acutely treated (Injection = Inj) with vehicle (0 mg/kg IP) or SR141716 (0.5, 2, 10 mg/kg IP). One hour later, half of the animals were killed for blood sampling (Blood) without further stressor exposure (Injection), the other half was exposed to the FST and killed 10 min after FST stressor onset (Injection + FST). n = 6–7 per group; *p < 0.05, **p < 0.01, ***p < 0.001 vs. respective vehicle group (0 mg/kg). #p < 0.05 vs. respective injection stress control group (Injection).