Altered SERT expression was associated with a significant reduction in depression-like behavior of IL6-KO in the Forced Swim Test (FST), the Sucrose Preference Test (SPT), the Novelty Suppressed Feeding Test (NSF) and blunted sensitivity to acute antidepressant treatment with the SSRI Escitalopram in the FST (Figure 2e–2g). This evidence concerns the gene SLC6A4 and major depressive disorder.