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This Article Full Text Full Text (PDF) All Versions of this Article: 293/5/H2995    most recent 00743.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Kindig, A. E. Articles by Kaufman, M. P. Search for Related Content PubMed PubMed Citation Articles by Kindig, A. E. Articles by Kaufman, M. P.

Blockade of purinergic 2 receptors attenuates the mechanoreceptor component of the exercise pressor reflex

Division of Cardiovascular Medicine, University of California Davis, Davis, California; and Penn State Heart & Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania

Submitted 27 June 2007 ; accepted in final form 28 August 2007

The finding that pyridoxalphosphate-6-azophenyl-2,4-disulfonic acid (PPADS), a P2 antagonist, attenuated the pressor response to calcaneal tendon stretch, a purely mechanical stimulus, raises the possibility that P2 receptors sensitize mechanoreceptors to static contraction of the triceps surae muscles. The mechanical component of the exercise pressor reflex, which is evoked by static contraction, can be assessed by measuring renal sympathetic nerve activity during the first 2–5 s of this maneuver. During this period of time, group III mechanoreceptors often discharge explosively in response to the sudden tension developed at the onset of contraction. In decerebrated cats, we, therefore, examined the effect of PPADS (10 mg/kg) injected into the popliteal artery on the renal sympathetic and pressor responses to contraction and stretch. We found that PPADS significantly attenuated the renal sympathetic response to contraction, with the effect starting 2 s after its onset and continuing throughout its 60-s period. PPADS also significantly attenuated the renal sympathetic nerve response to stretch, but did so after a latency of 10 s. Our findings lead us to conclude that P2 receptors sensitize group III muscle afferents to contraction. The difference in the onset latency between the PPADS-induced attenuation of the renal sympathetic response to contraction and the renal sympathetic response to stretch is probably due to the sensitivities of different populations of group III afferents to ATP released during contraction and stretch.

group III muscle afferents; group IV muscle afferents; ATP; cats; renal sympathetic nerve activity; neural control of the circulation

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