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PPADS attenuates the responses of group III and IV afferents to contraction with circulatory occlusion
Author(s) -
Kindig Angela Elizabeth,
Hayes Shawn G.,
Kaufman Marc P.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.lb36
Subject(s) - ppads , contraction (grammar) , reflex , circulatory system , muscle contraction , medicine , chemistry , endocrinology , anesthesia , anatomy , antagonist , receptor
ATP, by activating the P2 receptor on group III and IV afferents, is thought to evoke part of the exercise pressor reflex. PPADS, (P2 receptor antagonist) when injected into the arterial supply of skeletal muscle attenuated the reflex pressor response to contraction. In decerebrated cats we tested the hypothesis that injection of PPADS (10mg/kg) into the popliteal artery attenuated the responses of both group III (13) and group IV afferents (9) to contraction both with and without circulatory occlusion. Specifically, contraction with circulatory occlusion before PPADS increased the discharge of the group III afferents from 0.4 ± 0.1 to 1.2 ± 0.2 imp/s, whereas contraction afterwards increased the discharge from 0.4 ± 0.1 to only 0.9 ± 0.3 imp/s (P = .015). Likewise, contraction with circulatory occlusion before PPADS increased the discharge of the group IV afferents from 0.1 ± 0.06 to 0.4 ± 0.1 imp/s; afterwards PPADS abolished the response to contraction from 0.1 ± 0.06 to 0.1 ± 0.05 imp/s (P = 0.007). Similarly, contraction while the muscles were freely perfused before PPADS increased the discharge of the group III afferents from 0.1 ± 0.06 to 1.7 ± 0.5 imp/s. PPADS reduced this effect, discharge increasing from 0.2 ± 0.1 to only 1.1 ± 0.6 imp/s after PPADS (P = 0.002). Contraction under freely perfused conditions before PPADS increased the discharge of the group IV afferents from 0.09 ± 0.02 to 0.3 ± 0.09 imp/s, whereas after it had no effect on the discharge of these afferents (from 0.08 ± 0.04 to 0.1 ± 0.06 imp/s; P = 0.042). Our findings suggest that both group III and IV afferents are responsible for evoking the purinergic component of the exercise pressor reflex. Funding provided by NIH grant HL 30710.