BDNF and depressive disorder: For example, observation of rats placed under the forced swim test revealed that intra-VTA administration of BDNF led to a 57% increase in swimming, indicating the manifestation of depression, whereas disruption of BDNF neurotransmission due to truncated TrkB receptor in NAc results in a five-fold increase in time to reach immobility, indicating antidepressant effect [185].