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Effect of gadolinium, a stretch‐activated ion channel blocker, on the cardiovascular responses during dynamic exercise in cats
Author(s) -
Tsuchimochi Hirotsugu,
Hagihara Emi,
Nakamoto Tomoko,
Matsukawa Kanji
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.a572-c
Subject(s) - heart rate , treadmill , cardiology , medicine , cats , reflex , blood pressure , physical medicine and rehabilitation , endocrinology , physical therapy
Gadolinium (Gd 3+ ), a blocker of cation‐selective mechanosensitive channels, can be used as a tool to examine the mechanical component of the exercise pressor reflex. We have shown that the muscle mechanoreflex did not play a role in the initial cardiovascular adaptation during voluntary static exercise in conscious cats, because Gd 3+ unaffected the initial cardiovascular responses (Matsukawa et al., Am J Physiol 2007, in press). On the other hand, a role of the muscle mechanoreflex for the cardiovascular adaptation during dynamic exercise remained unsolved. We hypothesized that the mechanoreflex might contribute to the cardiovascular adaptation during dynamic exercise because of a greater amount of contracting muscle mass and of force produced as compared to those during static exercise. To test this hypothesis, we examined the effect of Gd 3+ on the increases in heart rate (HR) and mean arterial pressure (MAP) during treadmill exercise using conscious cats. The knee joint angle and pitch during exercise were measured as a means of the kinematic analysis of the hindlimb. As soon as exercise started, HR and MAP increased; their time courses at the initial 15‐s period of exercise were the same irrespective of running speed. HR and MAP gradually increased until the end of exercise. Gd 3+ (60 μmol/kg, ia) affected neither the baseline values nor the initial responses in HR and MAP at the onset of exercise. Gd 3+ also did not affect the changes in knee joint angle and pitch. We conclude that the cardiovascular adaptation during dynamic exercise is not predominantly induced by the muscle mechanoreflex. Feedforward control by central command descending from higher brain centers and/or feedback control by the muscle metaboreflex may explain the cardiovascular adaptation.