Yasuo Hisa, MD, Toshiyuki Uno, MD, Nobuhisa Tadaki, MD
Hitoshi Banba, MD, Shinobu Koike, MD

It is well known that calcitonin gene-related peptide (CGRP) plays an important role in the motor nervous system. We have already reported that there is a great difference between thyropharyngeal and cricopharyngeal muscles in the ratio of their motoneurons containing CGRP in the nucleus ambiguus (NA). In the present study, we clarified the ratio of laryngeal motoneurons containing CGRP using cholera toxin B subunit-conjugated gold (CTBG) as a retrograde tracer. In young dogs under deep anesthesia, CTBG was injected into the cricothyroid muscle (CT) in 3 dogs, in the thyroarytenoid muscle (TA) in 5 dogs, and in the posterior cricoarytenoid muscle (PCA) in 5 dogs. Dogs were reanesthetized and perfused with fixative 72 hours later. The brain stem was removed for silver enhancement and immunohistochemistry using the ABC method with anti-CGRP serum. The percentages of CGRP-immunoreactive motoneurons in the NA were as follows: CT, 93.0%; TA, 71.9%; and PCA, 85.5%. This difference in the CGRP immunoreactivity rate is considered to reflect the peculiar characteristics of each muscle and suggests that the innervation and/or the neurotrophic manner related to CGRP for each intrinsic laryngeal muscle is different.