Intramuscular nerve sprouting induced by CNTF is associated with increases in CGRP content in mouse motor nerve terminals

It is known that motor nerve terminal sprouting induced by either nerve injury or muscle paralysis is associated with an increase in calcitonin gene-related peptide (CGRP) content in the soma of motoneurons and in motor endplates. In the present study, CGRP-like immunoreactivity (CGRP-LI) was determined in motor endplates of animals in which nerve terminal sprouting had been induced by exogenous application of ciliary neurotrophic factor (CNTF). After 18 days of CNTF treatment we observed a significant increase in CGRP-LI in motor endplates. The results indicate that CGRP is upregulated when motor nerve outgrowth is induced, even in the absence of muscle paralysis or nerve lesion.