The effect of divergent selection on adrenocortical activity in Large White pigs on gene expression after ACTH, LPS and social stress challenges. E. Terenina1, C. Dugué1, E. Kulikova2, D. Bazovkina2, L. Gress1, G. Lefort1, Y. Billon3, C. Larzul1 & P. Mormede1 1 GenPhySE, INRA, INPT, ENSAT, Université de Toulouse, 31326 Castanet-Tolosan, France elena.mormede@inra.fr (Corresponding Author) 2 Department of Behavioral Neurogenomics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia 3 GenESI, INRA, Le Magneraud, 17700 Surgères, France The objective of the present experiment is to analyze the expression of candidate genes related to HPA axis and stress in the third generation of selection of two lines of pigs divergently selected on the basis of plasma cortisol levels measured one hour after injection of ACTH. This test allows to objectify the activity level of the hypothalamic-pituitary-adrenal (HPA) axis, a major neuroendocrine system of the stress response. The kinetics of the blood transcriptomic responses to adrenocorticotropic hormone (ACTH), lipopolysaccharide (LPS) and social stress were measured at 4 time points (0, 1h, 4h, and 24h after the challenge). Our results suggest that the responses to these different challenges are not affected in the same way by HPA axis activity. We found 22 differentially expressed genes for the inflammatory stress, 2 genes specific to the response to ACTH injection and 12 genes for the social stress. The expression of studied candidate genes did not differ according to the line. Four genes (MEGF9, S100A9, CERS4 and PSAP) were found to be differentially expressed in the three tests and could therefore be used for the overall study of stress response. With the financial support of the Agence Nationale de la Recherche, program ANR BIOADAPT, project SUSoSTRESS (ANR-12-ADAP-0008).