title: Allopregnanolone and social stress: regulation of the stress response in early pregnancy in pigs.
abstract: This experiment investigated whether allopregnanolone, a neurosteroid metabolite from progesterone, modulates the stress response during early pregnancy. Twenty-five nulliparous sows (Sus scrofa) were allocated to one of three treatments: pregnant, ovariectomized or ovariectomized administered daily intravenously with alfaxalone as a synthetic allopregnanolone analog. On days 5, 12 and 19 of pregnancy, all sows were subjected to social stress by submitting them individually to a resident-intruder test, acting as the intruder. Blood samples were collected to analyze plasma progesterone, allopregnanolone, cortisol and adrenocorticotropic hormone (ACTH) concentrations. On day 26, 10 sows across the three treatments were subjected to a dexamethasone suppression test followed by a corticotrophin-releasing hormone administration to test the functionality of their hypothalamo-pituitary-adrenal (HPA) axis through cortisol release. Pregnant sows returned more rapidly to baseline cortisol concentrations following the resident-intruder test (p = 0.006). However, there were no other differences in cortisol or ACTH concentrations according to treatment or day, or to the HPA responsivity test on day 26. Allopregnanolone concentration in pregnant sows was higher than in ovariectomized sows (p < 0.001), but stable during the first third of pregnancy. Allopregnanolone concentration was correlated with longer resident-intruder test duration (pregnant: r = 0.66, p = 0.0003; ovariectomized: r = 0.47, p = 0.03), reflecting lower aggressiveness, and with progesterone concentration (r = 0.25, p = 0.03). Alfaxalone administration raised plasma allopregnanolone concentration in alfaxalone-administered sows but resulted in little behavioral and physiological effects. These findings did not support the hypothesis that the stress response of the female pig changes in the first third of pregnancy. Allopregnanolone was associated with lower aggression in social encounters.
authors.affiliation: a Faculty of Veterinary and Agricultural Sciences , Animal Welfare Science Centre, University of Melbourne , Melbourne , Australia .
authors.forename: Jean-Loup
authors.initials: JL
authors.lastname: Rault
authors.affiliation: b South Australia Research and Development Institute , Roseworthy , Australia , and.
authors.forename: Kate
authors.initials: K
authors.lastname: Plush
authors.affiliation: c The Ritchie Centre, Monash Institute of Medical Research-Prince Henrys Institute of Medical Research , Clayton , Australia.
authors.forename: Tamara
authors.initials: T
authors.lastname: Yawno
authors.affiliation: b South Australia Research and Development Institute , Roseworthy , Australia , and.
authors.forename: Pieter
authors.initials: P
authors.lastname: Langendijk
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000187:drug effects*; D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D003346:Corticotropin-Releasing Hormone; D005260:Female; D006854:Hydrocortisone / Q000097:blood*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood / Q000187:drug effects*; D011277:Pregnanediones / Q000494:pharmacology*; D011280:Pregnanolone / Q000097:blood*; D011374:Progesterone / Q000097:blood*; D012931:Social Environment; D013315:Stress, Psychological / Q000097:blood*; D034421:Sus scrofa; D013552:Swine
chemical_list: D000777:Anesthetics; D011277:Pregnanediones; D011374:Progesterone; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; C006477:alphaxalone; D011280:Pregnanolone; D006854:Hydrocortisone
keywords: Aggression; HPA axis; alfaxalone; neurosteroid; progesterone; resident-intruder test