Involvement of α- and β-Adrenergic Receptors in Skeletal Muscle Blood Flow Changes During Hyper-/Hypocapnia in Anesthetized Rabbits
This study investigated the involvement of α1- and β2-adrenergic receptors in skeletal muscle blood flow changes during variations in ETCO2. Forty Japanese White rabbits anesthetized with isoflurane were randomly allocated to 1 of 5 groups: phentolamine, metaproterenol, phenylephrine, butoxamine, and atropine. Heart rate (HR), systolic blood pressure (SBP), common carotid artery blood flow (CCBF), masseter muscle tissue blood flow (MBF), and quadriceps muscle tissue blood flow (QBF) were recorded and analyzed at 3 periods: (1) baseline, (2) during hypercapnia (phentolamine and metaproterenol groups) or hypocapnia (phenylephrine, butoxamine, and atropine groups), and (3) during or after receiving vasoactive agents. MBF and QBF decreased during hypercapnia. The decrease in MBF was smaller than that in QBF. SBP and CCBF increased, while HR decreased. Both MBF and QBF recovered to their baseline levels after phentolamine administration. MBF became greater than its baseline level, while QBF did not fully recover after metaproterenol administration. MBF and QBF increased during hypocapnia. The increase rate in MBF was larger than that in QBF. HR, SBP, and CCBF did not change. Both MBF and QBF decreased to ∼90% to 95% of their baseline levels after phenylephrine or butoxamine administration. Atropine showed no effects on MBF and QBF. These results suggest the skeletal muscle blood flow changes observed during hypercapnia and hypocapnia may mainly involve α1-adrenergic but not β2-adrenergic receptor activity.Objective:
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Mean changes in muscle blood flow during hypercapnia and after phentolamine or metaproterenol administration.
MBF and QBF decreased during hypercapnia, while the decrease in MBF was smaller than that in QBF. Both MBF and QBF recovered to their baseline levels after phentolamine administration. In contrast, although MBF became greater than its baseline level, QBF did not fully recover to its baseline level after phentolamine administration. Data are expressed as the percentage change in respective baseline values. MBF, masseter muscle tissue blood flow; QBF, quadriceps muscle tissue blood flow. a P < .05 versus baseline; b P < .05 versus hypercapnia; c P < .05 between the 2 groups.
Mean changes in muscle blood flow during hypocapnia and after phenylephrine or butoxamine administration.
MBF and QBF increased during hypocapnia, while the increase in MBF was larger than that in QBF. Both MBF and QBF decreased to about 90% to 95% of their baseline levels after phenylephrine or butoxamine administration. Data are expressed as the percentage change in respective baseline values. MBF, masseter muscle tissue blood flow; QBF, quadriceps muscle tissue blood flow. a P < .05 versus baseline; d P < .05 versus hypocapnia; c P < .05 between the 2 groups.
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