Table 1.

Short summary of the direct receptorial effects of kynurenine pathway metabolites.

Kynurenine Pathway Metabolite	Receptorial Effect	References
l-Kynurenine	Aryl hydrocarbon receptor (AHR) agonist	[24]
Kynurenic acid	NMDA receptor antagonist	[36,37]
	Dual effect on AMPA receptors: partial agonist at low nanomolar concentrations; antagonist at high micromolar-millimolar concentrations	[39,40]
	Kainate receptor antagonist	[38]
	α7-nicotinic acetylcholine receptor antagonist	[41]
	G-protein coupled receptor 35 agonist	[42]
	AHR agonist	[33]
Cinnabarinic acid	Type 4 metabotropic glutamate receptor agonist	[60]
	AHR agonist	[61]
Quinolinic acid	NMDA agonist	[74]

NMDA: N-methyl-d-aspartate; AMPA: α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid.