Experimental reinnervation of a strap muscle with a few roots of the phrenic nerve in rabbits

In order to compare application of the roots of the phrenic nerve to the an sa hypoglossi for laryngeal muscle neurotization, I or more roots from the phrenic nerve were implanted into the right sternothyroid (RST) muscle of r abbits (n = 36). Controls were intact animals (in which RST innervation is provided by the ansa; n = 6) and denervated ones (n = 6), At 66 +/- 2 days (mean +/- SE) after neurotization, during quiet breathing, inspiratory elec tromyographic activity and isometric contraction force were observed in all reinnervated RST muscles (n = 24). During maximal inspiratory effort, elec tromyographic activity and force increased. In animals reinnervated by the C4 root alone, forces (46.27 +/- 7.8 g) were significantly higher than in i ntact animals (10.83 +/- 5.0 g). Retrograde labeling proved the phrenic ori gin of the neurotization. Electromyography of the diaphragm was recorded. W e conclude that in rabbits, neurotization of a strap muscle by 1 or 2 roots of the phrenic nerve allows inspiratory contraction, even during quiet bre athing. Such inspiratory activity is not observed in sternothyroid muscles of intact animals innervated by the ansa hypoglossi.