Downhill running preferentially increases CGRP in fast glycolytic muscle fibers.
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 alpha-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.
Homonko
D A
DA
The Toronto Hospital Research Institute, Toronto Western Division, Toronto, Ontario, Canada M5T 2S8.
Theriault
E
E
D000818:Animals; D000906:Antibodies; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes; D006003:Glycogen / Q000378:metabolism; D006019:Glycolysis / Q000502:physiology*; D009045:Motor Endplate / Q000378:metabolism; D009046:Motor Neurons / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology / Q000294:innervation / Q000502:physiology; D009218:Myosins / Q000032:analysis; D005082:Physical Exertion / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012420:Running / Q000502:physiology*; D013266:Stilbamidines
C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D000906:Antibodies; D005456:Fluorescent Dyes; D013266:Stilbamidines; D006003:Glycogen; D009218:Myosins; D015740:Calcitonin Gene-Related Peptide