Gender differences in the enhanced vulnerability of BDNF+/- mice to mild stress.

Two mild stress paradigms were used in the present study: acute (i.e. three injections of saline over 24 h) and subchronic (i.e. single daily injection of saline for 7 d). These mild stress procedures did not alter the behaviour of wild-type mice in the forced swim test. However, male BDNF+/- mice exhibited increased immobility in the forced swim test after mild stress. This genotypic difference in stress responsivity was also evident in plasma corticosterone levels after a single injection of saline. The behaviour of female mice of either genotype was not altered by mild stress, and there was no genotypic difference in the corticosterone response of female mice to a single saline injection. Male BDNF+/- mice should be a useful model in which to examine behavioural and neurochemical consequences of interactions among genetic and environmental factors implicated in stress-related affective disorders, such as major depression.