MGBA	microbiota–gut–brain axis
TyrDC	tyrosine decarboxylase
PD	Parkinson’s disease
GABA	gamma-aminobutyric acid
CNS	central nervous system
GI	gastrointestinal
ASD	autism spectrum disorder
ADHD	attention-deficit/hyperactivity disorder
ENS	enteric nervous system
EC	enterochromaffin cells
FMT	fecal microbiota transplantation