Table 2.

Peripheral LPS impacts peripheral and central tryptophan metabolism. Plasma and whole brain tissues collected 24h post-treatment were used to analyze the kynurenine pathway of tryptophan metabolism in response to peripheral immune stimulation. Tryptophan and kynurenine/tryptophan ratio were measured in the plasma (see Figure 3A for plasma kynurenine). Tryptophan, kynurenine/tryptophan ratio, and kynurenic acid (KA) were evaluated in the brain (see Figures 4B, 4C and 4E for brain kynurenine, 3-HK and QA respectively). Data represent sample means (SEM) and were analyzed using a two-ANOVA followed by the Holm-Sidak method for pairwise multiple comparisons. n = 5–8 samples/group.

		Genotype				Main Effects		Interaction
		BDNF+/+		BDNF+/−		Treatment	Genotype	Treatment × Genotype
	Metabolites (nM)	Saline	LPS	Saline	LPS	p-value	p-value
Plasma	Tryptophan	53.55 (6.6)	58.02 (5.4)	51.82 (4.3)	50.27 (5.4)	n.s.	n.s.	n.s.
	Kynurenine/ Tryptophan Ratio	0.013 (0.0009)	0.034 (0.002)	0.012 (0.001)	0.038 (0.006)	p<0.001	n.s.	n.s.
Brain	Tryptophan	46.45 (5.1)	45.54 (3.4)	42.95 (1.9)	55.29 (3.8)	n.s.	n.s.	n.s.
	Kynurenine/ Tryptophan Ratio	0.0078 (0.001)	0.019 (0.0008)	0.011 (0.004)	0.032 (0.004)	p<0.001	p<0.05	n.s.
	KA	0.46 (0.05)	0.30 (0.09)*	0.25 (0.04f	0.38 (0.03)	n.s.	n.s.	p<0.05

^*= main effect (treatment or genotype)

^#= post-hoc comparison between saline and LPS within the same genotype (BDNF^+/+ or BDNF^+/−)

⁺= post-hoc comparison between BDNF^+/+ and BDNF^+/− with the same treatment (saline or LPS)

^*,+,#p<0.05–0.01

^**,++,##p<0.01–0.001

^***,+++,###p<0.001