BDNF and major depressive disorder: The aim of the current study was to investigate the molecular changes in neurotrophin expression in Creb1TPH2CreERT2 and Creb1TPH2CreERT2Crem−/− mice after chronic fluoxetine treatment, with a focus on the brain structures implicated in depression pathology and with profound innervation by serotonergic projections – the PFC and hippocampus.