Mechanical Contraction Property of the Levator Veli Palatini Muscle

Abstract

Twenty adult dogs anesthetized with sodium pentobarbital were used as experimental animals in an analysis of the mechanical contraction properties of the levator veli palatini muscle. The following results were obtained: the contraction time and half relaxation time of maximal isometric twitch of the muscle were revealed to be 43 msec and 33 msec, respectively; a summation curve was obtained with stimulation at 15 Hz and maximal tetanic tension was at 70 Hz. The average of the tetanic tension ratio was found to be 5.7. The maximum rate of tension rise was observed at 150 Hz, and the value was twice the rate of the twitch contraction. The duration time of the active state plateau showed values of 3.9 to 4.5 msec. The contraction time of the levator veli palatini muscle closely resembles that of the intrinsic laryngeal and the orbicularis oris muscle.

The Behaviors of the Levator Veli Palatine Muscle Between 2 Surgical Conditions in Dog: The Comparison of Furlow and Pushback Methods

“…Gordon and Holbourn (1949) reported that the skeletal muscle strength decreased when muscles stretched. Kogo et al (1991) showed that velopharyngeal force declined when the LVP muscles of beagle dogs were stretched. In addition, another study reported that muscle strength increased as the muscle cross-sectional area became larger (Maughan et al, 1983).…”

“…In each animal, the LVP muscles were exposed without damaging the muscles, according to the method described in our previous paper (Kogo et al, 1991). The 18 beagle dogs were categorized into the following 4 groups (Figure 1): (1) the normal LVP group (N ¼ 5), whose LVP were exposed only.…”

“…In the overlapped sutured LVP group, the velopharynx is created carefully in size not to become smaller compared to The LVP were exposed without surgical damage (Kogo et al, 1991) in supine position fixed under sedation with tracheostomy. Following 4 different conditions were created.…”

“…We used bipolar silver-urethane wire hook electrodes (polar distance: 2 mm, diameter: 200 mm) with an input box and bioelectric amplifier (DAM50; World Precision Instruments), and implanted them into the LVP muscles on the right and left sides in the visible field, as per Kogo's method (Kogo et al, 1991). The surrounding tissues were covered with Vaseline.…”