抄録
Six adult cats weighing 2.2kg-4.7kg were anesthetized with intramusclar injection of ketamine hydrochloride. The left recurrent laryngeal nerve (RLN) was transsected at the level of the second tracheal ring and both cut ends were ligated. Electrically induced vocalization was performed after Kanai's method. (Horsley-Clarke coordinates AP : 0, L4.5-5.5, H-3.0--6.0) (stimulation 0.2ms, 50-100 μA, lasting 5-10s) Then EMG of the throarytenoid muscle (TA) and the posterior cricoarytenoid muscle (PCA) were recorded. Besides, single afferent discharges from laryngeal sensory receptors of paralyzed vocal cord were recorded during evoked vocalizations.
In this study, 25 weeks after transection of RLN the EMG of left TA showed recruitment, but the electromyographical activity of the left PCA was not observed. 20 weeks after neurorraphy of the left RLN and the left Ansa cervicalis, the activity of the left TA was almost the same as that of the control side. The EMG of left PCA showed the continuous activity during vocalization. However, in all cases, no return of vocal cord mobility was observed. The rate of single afferent discharge from laryngeal sensory receptors on paralyzed side was corresponded to fundamental frequency change during evoked vocalization. This result suggests that the central nervous system has received informations about paralyzed vocal cord vibrations from larynx during evoked vocalization.
