Dynamic exercise is associated with intensive ventilation, and therefore with functional loading of diaphragm, the principal inspiratory muscle in mammals. Numerous studies reported that aerobic exercise training induces adaptive changes in both muscle fibers and resistance arteries of locomotory muscles, but little attention has been paid to vessels of diaphragm. Exercise-induced vascular alterations are due to local and systemic, neural and humoral, influences, the latter being different during whole body exercise training and selective training of respiratory muscles. This study was aimed at comparing the effects o f 8-wk treadmill training (TT) and 8-wk airway obstruction (AO, produced by tracheal banding) on diaphragm feed arteries (DFA, 200-250 micron in diameter) in male Wistar rats. Reactivity of DFA segments was studied in isometric regimen. We found that TT resulted in an increase of VO_2max and oxidative capacity of gastrocnemius muscle compared to sedentary control. Oxidative enzymes activity in the diaphragm was not changed after TT, but was increased after AO. These characteristics of muscle tissue were mirrored in endothelium- dependent dilation of arteries to acetylcholine, which was not changed after TT, but increased after AO. The arteries of TT rats demonstrated reduced sensitivity to noradrenaline, but not to serotonin, non-adrenergic agonist. We speculate that selective suppression of adrenergic response is due to down-regulation of posjunctional adrenoceptors because of high sympathetic activity during bouts of exercise (as we showed earlier, DFA is densely innervated by sympathetic fibers). This explanation is supported by the fact, that DFA adrenoreactivity is not changed after AO. In conclusion, TT and AO result in different changes of DFA reactivity. In both cases the observed alterations are favorable for artery dilation during exercise but involve different mechanisms. Supported by the RFBR (grant 09-04- 01701-[acy]).