HTR1A and myalgic encephalomeyelitis/chronic fatigue syndrome: As an important clinical signature in ME/CFS patients regarding an elevated serum level of TGF-β1 reflecting the severity of fatigue [8, 57], we also found high level of plasma TGF-β1 in both models by chronic fluoxetine injection and 5-HT1A receptor-knockdown (Additional file 1: Fig. S4E and F).