Contribution of the dorsal branch of the accessory nerve to the innervation of the trapezius muscle in the pig - a retrograde tracing study.

The study was aimed to establish the contribution of the dorsal branch of the accessory nerve ( DBXI) to the innervation of the porcine trapezius muscle ( TRAP). Combined retrograde tracing using fluorescent tracer Fast blue ( FB) and surgical denervation procedure (excision of DBXI segment) were applied . FB+ neurons supplying the cervical (c- TRAP) and thoracic part (th- TRAP) of TRAP were localized in following nerve centres: the ipsilateral ventral horn of the grey matter of cervical neuromers, ipsilateral spinal ganglia and bilateral sympathetic chain ganglia. After the excision of DBXI segment, no FB+ motoneurons supplying c- TRAP were found while the mean number of those supplying th- TRAP was significantly decreased. A slight decrease in average numbers of sensory and autonomic neurons implemented in the innervation of both parts of TRAP was also observed. This study has revealed that in the pig DBXI is the only motor pathway to c- TRAP while the vast majority of motoneurons supplying porcine th- TRAP send their axons via DBXI. [ABSTRACT FROM AUTHOR]