Table 2.

Principal component analysis for all the parameters examined.

Parameter	Interpretation	Factor loading
		PC1	PC2	PC3
		− 47.77%	− 23.64%	− 12.12%
Dopamine	Nervous system	0.873	0.012	− 0.014
Noradrenaline	Nervous system	0.831	0.411	0.077
Adrenaline	Nervous system	0.739	0.592	0.071
d-ROM	Oxidative stress	0.648	− 0.539	0.190
BAP	Oxidative stress	0.568	− 0.124	0.348
IL-1β mRNA	Inflammation	0.466	− 0.542	0.543
TNF-α mRNA	Inflammation	0.324	− 0.778	0.441
IL-1β	Inflammation	0.803	0.553	0.125
IL-10	Inflammation	0.791	0.565	0.137
IL-2	Immune system	− 0.762	0.293	0.515
IL-5	Immune system	− 0.697	0.310	0.555
IL-17A	Immune system	− 0.575	0.553	0.435

Nervous system parameters (dopamine, noradrenaline, and adrenaline in peripheral blood); oxidative stress parameters (d-ROMs and BAP in peripheral blood); inflammation parameters (IL-1β and TNF-α mRNA, as well as IL-1β and IL-10 proteins in peripheral blood); and immune system parameters (IL-2, IL-5, and IL-17A proteins in peripheral blood) obtained from rats with or without a stress challenge were analyzed using principal component analysis (PCA). PC1, PC2, and PC3 represent the first, second, and third principal components of the set, respectively. Bold colored cells indicate factor loading values over 0.4 or less than − 0.4