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

Tibialis anterior (TA) muscles of rats underwent bilateral peroneal nerve 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, animals 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 muscle 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 returned to SO values but remained elevated (P < 0.05) in D muscle. Thus restoration of neural control of blood flow to resting muscle likely occurred by 21 days post-NC. Blood flow to stimulated muscle was not affected by NC or D, indicating the probable importance of metabolic factors in regulating blood flow during 1-Hz contractions. Cytochrome-c oxidase 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 animals returned to SO values, while values in denervated Th muscle continued to decrease. Despite these changes, endurance performance of TA muscle was not affected by D or NC at any time. These results suggest that reinnervation processes controlling blood flow and muscle function occur along similar time courses and that muscle blood flow is more closely related to endurance performance than is muscle oxidative capacity under these contraction conditions.