BLOOD-FLOW, MITOCHONDRIA, AND PERFORMANCE IN SKELETAL-MUSCLE AFTER DENERVATION AND REINNERVATION

Tibialis anterior (TA) muscles of rats underwent bilateral peroneal ne rve crush (NC) or denervation (D) and were compared with sham-operated (SO) animals to determine the effect of reinnervation on blood flow, mitochondria, metabolites, and muscle performance. After surgery, anim als were left for 2, 7, 21, or 42 days (NC and SO groups) or 2, 7, or 21 days (D group; n = 7-11.day(-1).group(-1)), after which TA muscles were stimulated in situ at 1 Hz. alpha-Motoneuron reinnervation of mus cle was complete 21 days after NC. Blood flow increased 10-fold above SO values in nonstimulated TA muscle 7 days after NC and D (P < 0.05). By 21 days, blood flow to nonstimulated TA muscle in NC animals retur ned to SO values but remained elevated (P < 0.05) in D muscle. Thus re storation of neural control of blood flow to resting muscle likely occ urred by 21 days post-NC. Blood flow to stimulated muscle was not affe cted by NC or D, indicating the probable importance of metabolic facto rs in regulating blood flow during 1-Hz contractions. Cytochrome-c oxi dase activity decreased (P < 0.05) below SO values 7 days after NC and D. By 21 days, cytochrome-c oxidase activity in TA muscles of NC anim als returned to SO values, while values in denervated Th muscle contin ued to decrease. Despite these changes, endurance performance of TA mu scle was not affected by D or NC at any time. These results suggest th at reinnervation processes controlling blood flow and muscle function occur along similar time courses and that muscle blood flow is more cl osely related to endurance performance than is muscle oxidative capaci ty under these contraction conditions.