TH and Parkinson disease: Modified Yeoldahanso-tang including Acorus gramineus Soland was reported to have neuroprotective effects in in vivo and in vitro studies; it could inhibit both the loss of tyrosine hydroxylase- (TH-) positive neurons in the SNpc and the reduction of the optical density of tyrosine hydroxylase-immunoreactive (TH-IR) fibers in the striatum in a C57BL/6 mice model of PD [21].