HCN1 and major depressive disorder: Although pathologic phenotype in WAG/Rij rats is genetically determined, previous data have shown that the absence epilepsy and depression-like comorbidity [28], as well as HCN1 (Ih) [23], can be altered by early postnatal environmental impacts (maternal care, neonatal maternal separation, and neonatal handling), indicating that epigenetic mechanisms might be involved.