Diaphragm plasticity following intrinsic laryngeal muscle denervation in rats.
OBJECTIVE
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 x cm(-2)). No independent training effect over and above the effects attributed to denervation of ILM were noted in ED animals.


CONCLUSIONS
The results highlight the role of vocal cord dilator function during both eupnea and exercise-induced hyperpnea.
Rodman
Joshua R
JR
Department of Physical Therapy, Exercise and Nutrition Sciences, State University of New York at Buffalo, Buffalo, NY 14214-3079, USA.
Gosselin
Luc E
LE
Horvath
Peter J
PJ
Megirian
David
D
Farkas
Gaspar A
GA
D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001835:Body Weight; D002950:Citrate (si)-Synthase / Q000032:analysis; D003964:Diaphragm / Q000502:physiology*; D007821:Laryngeal Muscles / Q000294:innervation*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D009121:Muscle Denervation; D018482:Muscle, Skeletal / Q000201:enzymology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
D002950:Citrate (si)-Synthase