TH and Parkinson disease: Since SN oxytocin receptor expression, but not striatum oxytocin receptor level was increased in the MPTP‐induced PD model and it was also correlated with the striatum TH level (Figure 1), we infer that the elevation of SN oxytocin receptor expression in the PD model may act to protect nigrostriatal DA signal.[36] We investigated the effect of knocking out SN oxytocin receptors on the vulnerability of the nigrostriatal DA signal.