A recent study in rats found that bilateral ET-1-induced lesion of the rat mPFC showed no change or reduced anxiety in the light–dark or OF test, but did show cognitive impairment.73 The robust behavioral phenotype obtained with discrete unilateral lesion in the left mPFC compared with larger bilateral lesions, could suggest that anxiety and depression phenotypes may be more pronounced for unilateral lesions, but this remains to be further tested. This evidence concerns the gene EDN1 and major depressive disorder.