TH and Parkinson disease: Lewy bodies (LBs) have been detected in the submucosal and myenteric layers of the GI system of PD patients mostly in the vasoactive intestinal peptide (VIP)-positive cholinergic neurons and minimally in tyrosine hydroxylase (TH)-positive neurons (Wakabayashi et al., 1988; Wakabayashi et al., 1989).