Calcitonin Gene-related Peptide-like Immunoreactive Motoneurons Innervating the Canine Inferior Pharyngeal Constrictor Muscle

Abstract

The percentage of the calcitonin gene-related peptide-immunoreactive motoneurons (Mn) in the nucleus ambiguus (NA) innervating the canine inferior pharyngeal constrictor muscle was examined using the cholera toxin B subunit-gold (CTBG) as a retrograde tracer and by immunohistochemistry. Labeled neurons with CTBG (CTBG MNs) from the thyropharyngeal muscle (TP) were located in the dorsomedial division of the rostral part of the NA and the average percentage of neurons with CGRP immunoreactivity was 70.3%. CTBG MNs from the cricopharyngeal muscle (CP) were located in the dorsal division of the rostral part of the NA and the average percentage of neurons with CGRP immunoreactivity was 21.2%. This low percentage of CGRP immunoreactivity is noteworthy and supports the idea that the CP is a particular striated muscle in function and innervation manner.