Abstract
We examined whether six wk (45min/d) of treadmill running (TT) moderates pituitary-adrenal cortical (PAC) responses and corticotropin-releasing factor[CRF] in microdissected nuclei (central nucleus of amygdala (CNA), paraventricular nucleus (PVN), median eminence (ME) to acute (10 min) heterotypic (novel) stress and no stress. Male Sprague-Dawley rats (N=24) were randomly assigned in a 2 GROUP (sedentary vs TT) *TEST(heterotypic-immobilization (IM) vs no stress (NS) *TIME (0,15,30,60 min) mixed factorial design with TEST and TIME repeated. After TEST, animals were returned to their home cages where blood was drawn (0.6ml) from a chronic indwelling jugular catheter. Plasma [ACTH] (pg/ml),[Corticosterone](CRT)(ug/dl) and [CRF] (pg/mg protein) were determined by radioimmunoassay. ANOVA and post hoc contrasts (p <.05) indicated a GROUP*TEST*TIME effect for ACTH. TT at 15 min (P=.04)(M=83.7, SD=14.2) and 30 min (P=.0038)(42.56,11.35) exhibited an attenuated ACTH effect compared with the sedentary controls min 15 (127.38, 28.5), min 30 (71.91,9.1) following heterotypic IM. A TEST effect was found for [CRT] and [ACTH].IM resulted in a greater PAC response compared with NS. ANOVA results indicated no difference (P>.4) in[CRF] between TT and sedentary in the CNA, PVN and ME regions. These data suggest a cross-stressor tolerance indicated by PAC hormones in male rats compared with previous findings of sensitization in estradiol-treated female rats. The failure of TT to moderate [CRF] in brain regions recognized to influence PAC responsiveness indicates the potential uniqueness of TT as a stressor and warrants further study.
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