Breed-specific expression of hippocampal 11β-hydroxysteroid dehydrogenases and glucocorticoid receptors in Erhualian and Pietrain pigs exhibiting distinct stress coping characteristics

The hippocampus may stimulate or inhibit the activity of HPA axis to maintain homeostasis during stress response, and its function is largely determined by the cytosol concentration of cortisol which is influenced by the balance between 11β-hydroxysteroid dehydrogenases 1 and 2 (11β-HSD1 and 2), as well as the number of glucocorticoid and mineralocorticoid receptor, GR and MR. However, it is unknown whether pigs exhibiting different stress coping characteristics display distinct patterns for hippocampal GR/MR and 11β-HSD1/2 expressions under both basal and stressed conditions. Therefore, 12 Erhualian (EHL) and 12 Pietrain (PIE) pigs were respectively allocated to control and 2 h transport groups and sacrificed to detect hippocampal expression of GR, MR, 11β-HSD1 and 11β-HSD2 mRNAs. Under basal conditions, EHL pigs exhibited higher GR, MR, and 11β-HSD1 but lower 11β-HSD2 in hippocampus compared with PIE pigs (P < 0.05), which resulted in a significantly higher ratio of 11β-HSD1/11β-HSD2 (P < 0.05). A significantly lower GR (P < 0.05) and a tendency of lower MR (P = 0.1) mRNA expression was detected in the transport group of EHL pigs compared with their control counterparts, resulting in an unaltered GR/MR ratio. In contrast, the transport group of PIE pigs exhibited a significantly higher GR/MR ratio (P < 0.05). These results indicate a significant breed-specific hippocampal sensitivity or responsitivity to glucocorticoids, which may account, to some extent, for the different basal cortisol levels and stress coping characteristics of these two breeds of pigs.