CALCITONIN-GENE-RELATED PEPTIDE-LIKE IMMUNOREACTIVE MOTONEURONS INNERVATING THE CANINE INFERIOR PHARYNGEAL CONSTRICTOR MUSCLE

The percentage of the calcitonin gene-related peptide-immunoreactive m otoneurons (Mn) in the nucleus ambiguus (NA) innervating the canine in ferior pharyngeal constrictor muscle was examined using the cholera to xin B subunit-gold (CTBG) as a retrograde tracer and by immunochistoch emistry. Labeled neurons with CTBG (CTBG MNs) from the thyropharyngeal muscle (TP) were located in the dorsomedial division of the rostral p art of the NA and the average percentage of neurons with CGRP immunore activity was 70.3%. CTBG MNs from the cricopharyngeal muscle (CP) were located in the dorsal division of the rostal part of the NA and the a verage percentage of neurons with CGRP immunoreactivity was 21.2%. Thi s low percentage of CGRP immunoreactivity is noteworthy and supports t he idea that the CP is a particular striated muscle in function and in nervation manner.