title: Exercise training changes autonomic cardiovascular balance in mice.
abstract: Experiments were performed to investigate the influence of exercise training on cardiovascular function in mice. Heart rate, arterial pressure, baroreflex sensitivity, and autonomic control of heart rate were measured in conscious, unrestrained male C57/6J sedentary (n = 8) and trained mice (n = 8). The exercise training protocol used a treadmill (1 h/day; 5 days/wk for 4 wk). Baroreflex sensitivity was evaluated by the tachycardic and bradycardic responses induced by sodium nitroprusside and phenylephrine, respectively. Autonomic control of heart rate and intrinsic heart rate were determined by use of methylatropine and propranolol. Resting bradycardia was observed in trained mice compared with sedentary animals [485 +/- 9 vs. 612 +/- 5 beats/min (bpm)], whereas mean arterial pressure was not different between the groups (106 +/- 2 vs. 108 +/- 3 mmHg). Baroreflex-mediated tachycardia was significantly enhanced in the trained group (6.97 +/- 0.97 vs. 1.6 +/- 0.21 bpm/mmHg, trained vs. sedentary), whereas baroreflex-mediated bradycardia was not altered by training. The tachycardia induced by methylatropine was significantly increased in trained animals (139 +/- 12 vs. 40 +/- 9 bpm, trained vs. sedentary), whereas the propranolol effect was significantly reduced in the trained group (49 +/- 11 vs. 97 +/- 11 bpm, trained vs. sedentary). Intrinsic heart rate was similar between groups. In conclusion, dynamic exercise training in mice induced a resting bradycardia and an improvement in baroreflex-mediated tachycardia. These changes are likely related to an increased vagal and decreased sympathetic tone, similar to the exercise response observed in humans.
authors.affiliation: Hypertension Unit, Heart Institute University of São Paulo, Medical School, 05403-000 São Paulo, Brazil.
authors.forename: K
authors.initials: K
authors.lastname: De Angelis
authors.forename: R B
authors.initials: RB
authors.lastname: Wichi
authors.forename: W R A
authors.initials: WR
authors.lastname: Jesus
authors.forename: E D
authors.initials: ED
authors.lastname: Moreira
authors.forename: M
authors.initials: M
authors.lastname: Morris
authors.forename: E M
authors.initials: EM
authors.lastname: Krieger
authors.forename: M C
authors.initials: MC
authors.lastname: Irigoyen
mesh_terms: D000818:Animals; D001286:Atropine Derivatives / Q000494:pharmacology; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight; D002319:Cardiovascular System / Q000294:innervation*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010805:Physical Conditioning, Animal; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology; D011433:Propranolol / Q000494:pharmacology; D012149:Restraint, Physical
chemical_list: D001286:Atropine Derivatives; C006649:methylatropine; D011433:Propranolol