Selective denervation of the Musculus pectoralis muscle in the chicken

A surgical method for selective denervation was developed to facilitate investigations about the postmortem characteristics of denervated pectoralis muscles in chickens, Musculus (M.) pectoralis. The M. pectoralis was denervated in anesthetized chickens unilaterally or bilaterally by excising a 1-cm section of the nervus pectoralis as it branched from the N. medianoulnaris in the brachial plexus. Denervation resulted in significant (P less than .01) and consistent depression in the relative weight of M. pectoralis from the wk 2 through 17 postoperative. The relative weight of the functionally antagonistic M. supracoracoideus was unaffected by ipsilateral denervation of the M. pectoralis. The M. coracobrachialis acts in synergism with the M. pectoralis and displayed significant muscle atrophy at 4, 6, 8 and 17 wk postoperative in treatment groups where the ipsilateral M. pectoralis was denervated. Only the M. pectoralis displayed histological signs of denervation in transverse cryostat sections. Denervated tissue was characterized by atrophic and rounded muscle-fiber profiles, an increase in the endomysial and perimysial connective-tissue spaces, and leucocytes within degenerative perimysial nerves from 2 through 17 wk postoperative. Signs of denervation were distributed throughout seven zones sampled from the M. pectoralis. This study indicated that selective denervation of the M. pectoralis was achieved and that postoperative histology was necessary to accurately assess denervation.