Abstract:

Objective  To study obstructive sleep apnea(OSA)and the effect of mandibular advancement device(MAD) on the structure and function of the hypoglossal nerve by establishing a New Zealand white rabbit model of obstructive sleep apnea(OSA), in order to provide a theoretical basis for the further study of hypoglossal nerve and precision treatment of OSA.

Methods  Eighteen 6-month-old male New Zealand white rabbits were randomly divided into control group, OSA group and MAD group. The rabbits were induced to sleep in supine position for 2 h every day, and general anesthesia was performed after 8 weeks. One side of hypoglossal nerve and genioglossal muscle were passively separated and exposed. Using signal acquisition and processing system, Taimeng BL-420F, the threshold intensity of genioglossal muscle contraction caused by stimulating hypoglossal nerve, the single contraction ability of genioglossal muscle when stimulating hypoglossal nerve intensity was 0.5 V and the latency of genioglossal muscle contraction caused by stimulating hypoglossal nerve were recorded. The threshold intensity, genioglossus contraction tension and latency of the three groups were compared. The hypoglossal nerve tissue specimen was prepared on the other side, and the tissue structure of nerve fibers was observed under optical microscope.

Results  The threshold stimulation in OSA group was higher than that in control group and MAD group, the genioglossus contraction tension was lower than that in control group and MAD group, and the latency was longer than that in control group and MAD group(P＜0.05). There was no significant difference in threshold stimulation, genioglossus contraction tension and latency between control group and MAD group(P＞0.05). The nerve fibers in the control group had no obvious changes, the nerve fiber tissue structure was complete, the cells were arranged in layers, the nerve fiber tissue structure was closely arranged, and there was no obvious liquefaction, degeneration and necrosis. In OSA group, the hypoglossal nerve fibers showed degeneration to varying degrees, which showed that the nerve fibers were arranged disorderly, dissolved and denatured, and even condensed. The disorder and degeneration of nerve fibers in MAD group were milder than those in OSA group.

Conclusion  OSA can reduce the conduction performance of the hypoglossal nerve and the contractible tension of the genioglossus muscle in OSA rabbits. OSA can lead to the disordered arrangement and even degeneration of the nerve fibers. MAD therapy can reduce the damage to the hypoglossal nerve caused by OSA and play a protective role in hypoglossal nerve.

Key words: sleep apnea, obstructive, hypoglossal nerve, mandibular advancement device