Attenuated blood pressure responsiveness during post-exercise hypotension.
OBJECTIVE
To test the hypotheses that acute treadmill exercise would produce post-exercise hypotension (PEH) and that PEH would be associated with reduced mean arterial pressure (MAP) responsiveness to the alpha 1-adrenergic agonist phenylephrine.


METHODS
Arterial and venous catheters were implanted into exercise-trained female Dahl-salt sensitive rats (n = 9) for measurement of pulsatile blood pressure (BP) and heart rate (HR). The changes in BP following ganglionic blockade (hexamethonium/atropine) and the MAP responses to phenylephrine (PE) injections after ganglionic blockade (GB) were examined on separate days in testing cages (control) and following 40 min of treadmill exercise (post-ex).


RESULTS
Thirty minutes following graded treadmill exercise (20-40 m/min, 0% grade, 40 min duration) blood pressure was significantly reduced (-9 +/- 1) mmHg compared to control. After exercise, GB produced a 43 +/- 3 mmHg decrease in BP which tended (p = 0.08) to be less than the reduction observed during control studies (51 +/- 2 mmHg). PE-induced increases in BP were significantly lower post-ex than control for each of the dosages tested (0.5, 1.0 and 2.0 micrograms/kg).


CONCLUSIONS
These results demonstrate that there is sustained reduction in PE-induced MAP responsiveness which accompanies exercise-induced decreases in blood pressure in the Dahl salt-sensitive rat. Thus, decreased alpha-adrenoceptor responsiveness may contribute to the production of PEH.
VanNess
J M
JM
Department of Nutrition, Food, and Movement Sciences, Florida State University, Tallahassee 32306-4079, USA.
Takata
H J
HJ
Overton
J M
JM
D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D005260:Female; D007022:Hypotension / Q000209:etiology / Q000503:physiopathology*; D007275:Injections, Intravenous; D010656:Phenylephrine / Q000008:administration & dosage*; D010805:Physical Conditioning, Animal / Q000009:adverse effects*; D051381:Rats
D000316:Adrenergic alpha-Agonists; D010656:Phenylephrine