HTR2A and hydrops fetalis: In contrast to the 5-HT1A receptor, the major excitatory serotonin receptor 5-HT2A was shown to be downregulated by chronic rTMS in rats [73]; interestingly, in humans, decrease of 5-HT2A receptors in the hippocampus and the bilateral DLPFC was correlated with treatment response to HF rTMS [74].