Contractile properties of the tongue muscles: effects of hypoglossal nerve and extracellular motoneuron stimulation in rat

Abstract

1. Stimulation of the whole hypoglossal (XIIth) nerve or its medial or lateral branch in the rat produced two major movements of the tongue as measured with a single force transducer attached to the tip of the tongue. Stimulation of the whole XIIth nerve or the lateral branch produced a retrusion of the tongue, whereas stimulation of the medial branch produced a protrusion. 2. The average retrusive twitch tension evoked by stimulation of the XIIth nerve (11.25 g) or the lateral branch (12.02 g) was significantly greater (P < or = 0.0001) than the protrusive twitch tension (1.05 g) elicited by medial branch stimulation. The tetanic tension produced by lateral branch stimulation (36.82 g) was significantly greater (P < or = 0.007) than the whole nerve tetanic tension (28.23 g). The greater tension elicited by stimulation of the lateral branch of the nerve when compared with the tension elicited by stimulation of the whole XIIth nerve was probably due to the absence of protrusive axons in the lateral branch of the nerve. Stimulation of the whole XIIth nerve activates axons innervating both protrusive and retrusive muscles, resulting in a weaker net retrusive force. 3. The contraction time of the tongue in response to medial branch stimulation (10.94 ms) was significantly faster than when the whole XIIth nerve (15.68 ms, P < or = 0.007) or lateral branch (13.36 ms, P < or = 0.05) was stimulated. The twitch contraction time of the tongue in response to whole XIIth nerve or lateral branch stimulation was not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Co‐activation of tongue protrudor and retractor muscles during chemoreceptor stimulation in the rat

“…co-activating the tongue protrudor and retractor muscles) caused tongue retraction in human subjects (Eisele, Smith, Alam & Schwartz, 1997). Consistent with these data, Gilliam & Goldberg (1995), using a rat model, found that the retractor muscles produce 10-20 times more force than the GG muscle, which explains why co-activation of both muscles results in strong tongue retraction. Thus, in both humans and rats, when protrudor and retractor muscle groups are activated maximally and 1.…”

“…The trachea was cannulated caudal to the larynx to ensure airway patency during the surgery and to permit subsequent tracheal occlusions. The GG and HG muscles, and XIIth nerves were exposed bilaterally using a ventral approach (Gilliam & Goldberg, 1995). Following isolation, the XIIth nerves were bathed in mineral oil.…”

“…EMG activities of the GG, HG and diaphragm (Dia) were recorded by inserting two fine wire (diameter, 0·125 mm; Formvar, California Fine Wire) electrodes into each muscle (Fregosi, 1994 (Gilliam & Goldberg, 1995;Fig. 1).…”

“…Accordingly, the present experiments were designed to test the hypothesis that progressive increases in respiratory drive are associated with co-activation of the extrinsic tongue muscles, and retraction of the tongue. This was done by adapting the model of Gilliam & Goldberg (1995), which allowed us to make simultaneous measurements of tongue muscle force and the neural drive to both tongue protrudor and retractor muscles during breathing in anaesthetized, tracheotomized rats. Our hypothesis was confirmed, and the significance of these observations for the maintenance of pharyngeal airway patency during spontaneous breathing is discussed.…”

Multifunctional Laryngeal Motoneurons: an Intracellular Study in the Cat

“…Bipolar silver cuff electrodes were placed around the C5 phrenic, L1 abdominal, and lateral branch of the hypoglossal (lat-X II) nerves for recording, around both SL Ns for recording and stimulation, and around both RL Ns for stimulation. The lat-X II innervates the styloglossus muscle, i.e., the elevator of the posterior tongue (Gilliam and Goldberg, 1995). Activities of these nerves were amplified, f ull-wave rectified, and low-pass filtered (time constant, 1 msec).…”