Role played by purinergic receptors on muscle afferents in evoking the exercise pressor reflex.
The exercise pressor reflex is believed to be evoked, in part, by multiple metabolic stimuli that are generated when blood supply to exercising muscles is inadequate to meet metabolic demand. Recently, ATP, which is a P2 receptor agonist, has been suggested to be one of the metabolic stimuli evoking this reflex. We therefore tested the hypothesis that blockade of P2 receptors within contracting skeletal muscle attenuated the exercise pressor reflex in decerebrate cats. We found that popliteal arterial injection of pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS; 10 mg/kg), a P2 receptor antagonist, attenuated the pressor response to static contraction of the triceps surae muscles. Specifically, the pressor response to contraction before PPADS averaged 36 +/- 3 mmHg, whereas afterward it averaged 14 +/- 3 mmHg (P < 0.001; n = 19). In addition, PPADS attenuated the pressor response to postcontraction circulatory occlusion (P < 0.01; n = 11). In contrast, popliteal arterial injection of CGS-15943 (250 micro g/kg), a P1 receptor antagonist, had no effect on the pressor response to static contraction of the triceps surae muscles. In addition, popliteal arterial injection of PPADS but not CGS-15943 attenuated the pressor response to stretch of the calcaneal (Achilles) tendon. We conclude that P2 receptors on the endings of thin fiber muscle afferents play a role in evoking both the metabolic and mechanoreceptor components of the exercise pressor reflex.
Hanna
Ramy L
RL
Division of Cardiovascular Medicine, Departments of Internal Medicine and Human Physiology, University of California, Davis, California 95616, USA. rlhanna@ucdavis.edu
Kaufman
Marc P
MP
D000125:Achilles Tendon / Q000502:physiology; D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology*; D002415:Cats; D003655:Decerebrate State; D007269:Injections, Intra-Arterial; D009043:Motor Activity / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000098:blood supply / Q000294:innervation*; D009475:Neurons, Afferent / Q000502:physiology*; D011150:Popliteal Artery; D011732:Pyridoxal Phosphate / Q000008:administration & dosage / Q000031:analogs & derivatives*; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects; D013314:Stress, Mechanical
D018048:Receptors, Purinergic P2; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate