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The role of acid sensing ion channels in the exercise pressor reflex
Author(s) -
Hayes Shawn G.,
Kindig Angela E.,
Kaufman Marc P.
Publication year - 2007
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.21.5.a570-d
Subject(s) - amiloride , acid sensing ion channel , lactic acid , contraction (grammar) , reflex , chemistry , medicine , endocrinology , myogenic contraction , muscle contraction , pharmacology , sodium , ion channel , biology , receptor , organic chemistry , smooth muscle , bacteria , genetics
Lactic acid activates thin fiber afferents evoking the exercise pressor reflex. We hypothesized that hydrogen ions associated with lactic acid accumulation in the exercising muscle act on acid sensing ion channels (ASIC) on thin muscle afferents. To test this hypothesis we examined in decerebrate cats if amiloride, an ASIC blocker, attenuated the pressor and cardioaccelerator responses to static contraction, to tendon stretch and to arterial injections of lactic acid and capsaicin. We established a dose of amiloride (0.5 μg/kg; i.a.) that blocked the pressor and cardioaccelerator responses to contraction and lactic acid injection but had no effect on the responses to stretch and capsaicin. A higher dose of amiloride (5 μg/kg, i.a.) not only attenuated the pressor and cardioaccelerator responses to lactic acid and contraction, but also attenuated the responses to stretch and to capsaicin, maneuvers in which ASIC play no significant role. The low dose of amiloride (0.5 μg/kg) had no effect on the discharge of muscle spindles in response of tendon stretch and injection of succinylcholine whereas the high dose (5 μg/kg) attenuated the responses to both. Our data suggest the low dose of amiloride selectively blocked ASIC whereas the high dose blocked ASIC and impulse conduction in muscle afferents. We conclude that ASIC play a role in the metabolic, but not the mechanical, component of the exercise pressor reflex.