Treadmill exercise training augments brain norepinephrine response to familiar and novel stress

In a test of hypothalamic-pituitary-adrenal (HPA) cortical and hypothalamic -pituitary-gonadal (HPG) interaction during familiar and novel stress, we p reviously reported that treadmill exercise training led to blunted plasma a drenocorticotrophin (ACTH) response to acute treadmill running but a hyper- responsiveness of ACTH after novel immobilization, In this follow-up analys is, we examined whether those results might be plausibly explained by a sim ilar effect of treadmill exercise training on increased levels of norepinep hrine (NE) in hypothalamic and limbic brain regions which synergize to modu late the release of ACTH during stress. Ovariectomized Sprague-Dawley rats that had been exercise trained by treadmill running or remained sedentary f or 6 weeks received intramuscular injections of estradiol benzoate (Eb) or sesame oil on each of 3 days prior to 15 min of familiar treadmill running or novel immobilization. Treadmill exercise training, regardless of Eb trea tment or type of stress, increased NE levels in the paraventricular (PVN), arcuate, medial preoptic, and ventromedial areas of the hypothalamus and pr otected against depletion of NE in the locus coeruleus, amygdala, and hippo campus, We conclude that treadmill exercise training has a hyperadrenergic effect in brain areas that modulate hypothalamic regulation of ACTH release during stress that is independent of HPA-HPG interaction and novelty of th e stressor. To help elucidate these findings, the effects of treadmill exer cise training on A1-A2 nuclei which innervate the PVN and their relationshi p with the limbic and hypothalamic responses we report require study, (C) 2 000 Elsevier Science Inc.