3-HAA	3-hydroxyanthranilic acid
3-HK	3-hydroxykynurenine
5-HT	Serotonin
α7nAChR	α7 nicotinic acetylcholine receptors
αSyn	α-synuclein
AChEI	acetylcholinesterase inhibitor
AD	Alzheimer’s Disease
ADAS-cog	Cognitive Alzheimer’s Disease Assessment Scale
AMPA	α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid
ApoaA1	apolipoprotein A1
BBB	Blood–Brain Barrier
BuChE	butyrylcholinesterase
CSF	cerebrospinal fluid
DBS	Deep Brain Stimulation
DLPFC	dorsolateral prefrontal cortex
EGF	Epidermal Growth Factor
FAB	Frontal Assessment Battery
FDA	Food and Drug Administration
GPR35	G-protein-coupled receptor
HCs	healthy controls
IDO	indoleamine 2,3-dioxygenase
INF-γ	interferon-gamma
KAT	kynurenine aminotransferase
KMO	kynurenine 3-monooxygenase
KP	kynurenine pathway
KYNA	Kynurenic acid
LAT-1	L-amino acid transporter
LPS	Lipopolysaccharides
MDD	Major Depressive Disorder
MMSE	Mini-Mental State Examination
NAC	N-acetylcysteine
NAD+	nicotinamide adenosine dinucleotide
NMDA	N-methyl-D-aspartate
PAM	positive allosteric modulator
PD	Parkinson’s Disease
PD-MDCI	mild cognitive impairment in PD
PDD	Parkinson’s Disease Dementia
PIC	picolinic acid
QUIN	quinolinic acid
RCTs	Randomized Controlled Trials
ROS	Reactive Oxygen Species
SNpc	substantia nigra pars compacta
TDAS	transcranial direct or alternating stimulation
TDO	tryptophan 2,3-dioxygenase
TLRS	Toll-like receptors
TMS	Transcranial Magnetic Stimulation
TRP	tryptophan