Downhill running preferentially increases CGRP in fast glycolytic muscle fibers

• Published in: Journal of applied physiology (1985) Vol. 89; no. 5; pp. 1928 - 1936
• Main Authors: Homonko, Darlene A, Theriault, Elizabeth
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.11.2000; American Physiological Society
• Subjects: Animals; Antibodies; Biological and medical sciences; Calcitonin Gene-Related Peptide - analysis; Calcitonin Gene-Related Peptide - immunology; Calcitonin Gene-Related Peptide - metabolism; Exercise; Female; Fluorescent Antibody Technique; Fluorescent Dyes; Fundamental and applied biological sciences. Psychology; Glycogen - metabolism; Glycolysis - physiology; Motor Endplate - metabolism; Motor Neurons - physiology; Muscle Fibers, Fast-Twitch - chemistry; Muscle Fibers, Fast-Twitch - metabolism; Muscle, Skeletal - cytology; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Muscular system; Myosins - analysis; Neurons; Peptides; Peripheral nervous system. Autonomic nervous system. Neuromuscular transmission. Ganglionic transmission. Electric organ; Physical Exertion - physiology; Rats; Rats, Wistar; Running - physiology; Stilbamidines; Vertebrates: nervous system and sense organs; Physical exercise; Vertebrata; Mammalia; Rat; Rodentia; Plasticity; Motor neuron; Muscular fiber; Striated muscle; Calcitonine gene related peptide; Neuropeptide; Neuromuscular junction
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.2000.89.5.1928

The Toronto Hospital Research Institute, Toronto Western Division, Toronto, Ontario, Canada M5T 2S8 Calcitonin gene-related peptide (CGRP) is present in some spinal cord motoneurons and at neuromuscular junctions in skeletal muscle. We previously reported increased numbers of CGRP-positive (CGRP+) motoneurons supplying hindlimb extensors after downhill exercise (Homonko DA and Theriault E, Inter J Sport Med 18: 1-7, 1997). The present study identifies the responding population with respect to muscle and motoneuron pool and correlates changes in CGRP with muscle fiber type-identified end plates. Twenty seven rats were divided into the following groups: control and 72 h and 2 wk postexercise. FluoroGold was injected into the soleus, lateral gastrocnemius, and the proximal (mixed fiber type) or distal (fast-twitch glycolytic) regions of the medial gastrocnemius (MG). Untrained animals ran downhill on a treadmill for 30 min. The number of FluoroGold/CGRP+ motoneurons within proximal and distal MG increased by 72 h postexercise ( P  < 0.05). No significant changes were observed in soleus or lateral gastrocnemius motoneurons postexercise. The number of -bungarotoxin/CGRP+ motor end plates in the MG increased exclusively at fast-twitch glycolytic muscle fibers 72 h and 2 wk postexercise ( P  < 0.05). One interpretation of these results is that unaccustomed exercise preferentially activates fast-twitch glycolytic muscle fibers in the MG. neuropeptides; neuromuscular plasticity; activity; rat