RODMAN, J. R., L. E. GOSSELIN, P. J. HORVATH, D. MEGIRIAN, and G. A. FARKAS. Diaphragm plasticity following intrinsic laryngeal muscle denervation in rats. Med. Sci. Sports Exerc., Vol. 34, No. 2, pp. 251–257, 2002.
Purpose: During inspiration, recruitment of the intrinsic laryngeal muscles (ILM) reduces the inspiratory load on the ventilatory pump muscles. The purpose of our study was to determine 1) whether the diaphragm adapts to denervation of the ILM, and 2) whether the additional stimulus of exercise training affects the degree to which the diaphragm adapts to ILM denervation.
Methods: Thirty-six male Sprague-Dawley rats (2 months) were randomly divided into sedentary control (SC), sedentary-denervated (SD), and exercise-denervated (ED) groups. Control animals underwent sham operations, whereas ILM-denervated animals underwent bilateral transection of the recurrent laryngeal nerves. Three weeks after surgery, animals in the ED group performed a treadmill training protocol for a period of 6 wk.
Results: Denervation (SD and ED animals) of the ILM significantly increased diaphragm citrate synthase activity (20%), in vitro endurance, and time to peak twitch tension (15%), and reduced (13%) peak tetanic tension (Po, N·cm−2). No independent training effect over and above the effects attributed to denervation of ILM were noted in ED animals.
Conclusion: The results highlight the role of vocal cord dilator function during both eupnea and exercise-induced hyperpnea.
Department of Physical Therapy, Exercise and Nutrition Sciences, State University of New York at Buffalo, Buffalo, NY 14214-3079
Submitted for publication September 2000.
Accepted for publication May 2001.