DEGENERATION OF MOTOR-NERVE FIBERS ENHANCES THE EXPRESSION OF CALCITONIN GENE-RELATED PEPTIDE IN RAT SENSORY NEURONS

Calcitonin gene-related peptide (CGRP) in skeletal muscle is of neural origin. After degeneration of sensory fibers induced by removal of th e lumbar dorsal root ganglia (DRG), the CGRP content in the rat soleus muscle was reduced to about 5% of the normal level. In contrast, dege neration of motor fibers induced by sectioning of the lumbar ventral r oots markedly increased the CGRP content in the soleus muscle and CGRP levels in the lumbar DRG. It is suggested that the expression of CGRP in sensory neurons is up-regulated by some humoral factor induced by degeneration of motor nerve fibers.