Calcitonin gene-related peptide immunoreactivity at the human neuromuscular junction

We have studied the presence of calcitonin gene-related peptide (CGRP) immunoreactivity at the human motor end-plate in intercostal muscles from 6 normal subjects. Only a small proportion of end-plates were positively stained in the muscle. Different metabolic states at single motor end-plates or variable rates of CGRP synthesis in separate motoneurones could account for the uneven distribution of CGRP immunoreactivity at the human neuromuscular junction, or else, extremely low amounts of the peptide are below the threshold of sensitivity of the immunofluorescence method used in the present study.