TREADMILL EXERCISE TRAINING AND ESTRADIOL INCREASE PLASMA ACTH AND PROLACTIN AFTER NOVEL FOOTSHOCK

We examined whether rats that were treadmill exercise trained (Tr) or chronically immobilized (CI) had similar responses by the hypothalamic -pituitary-adrenal (HPA) cortical axis to acute stress and whether the HPA responses interacted with the hypothalamic-pituitary-gonadal (HPG ) axis. After 6 wk (1 h/day, 6 days/wk) of Tr or CI, plasma concentrat ions of adrenocorticotropic hormone ([ACTH]), [prolactin], and [cortic osterone] were measured after familiar (treadmill running or immobiliz ation) or novel (footshock) stress. Ovariectomized Sprague-Dawley fema les (n = 72) were implanted with capsules containing estradiol benzoat e (E(2)) and randomly assigned in a 2-group (E(2) vs. no E(2)) x 3 tre atment (Tr vs. CI vs. sedentary) x 4 acute stressor [footshock vs. tre admill running (Run) vs. immobilization (Im) vs. no stress] x 3 recove ry time (1 vs. 15 vs. 30 min) mixed-model analysis of variance. E(2) c apsules were removed from one-half of the animals 48 h before the firs t stressor session. After 10 min of acute stress, blood was drawn from a jugular catheter at 1, 15, and 30 min of recovery. [ACTH] and [prol actin] after footshock were higher in Tr rats with E(2) compared with CI and sedentary rats without E(2); recovery levels for sedentary anim als were higher after Run compared with Im. The elevation in [corticos terone] from minute 1 to 15 of recovery was higher after the familiar Run and Im conditions. Our findings are consistent with an increased r esponsiveness of the HPA axis to novel footshock after treadmill exerc ise training that is additionally modulated by the HPG axis.