Effects of Nasal Obstruction on Maturation of the Jaw-opening Reflex in Growing Rats

Objective: Nasal obstruction during growth changes craniofacial morphology and function. However, the etiological mechanisms of these changes are unknown. The aim of the present study was to investigate the effects of nasal obstruction during growth on the maturation of the jaw-opening reflex (JOR) using an electrophysiological technique. We focused on the oral sensory receptors that regulate the activities and reflexes of the orofacial muscles.

Design: Sixty 6-day-old male Wistar rats were randomly divided into control and experimental groups (n = 30 each). The experimental group underwent unilateral nasal obstruction at 8 days of age. The JOR was evoked by bilateral, low-intensity electrical stimulation of the inferior alveolar nerve. The electromyographic responses were recorded bilaterally from the digastric muscles at 5, 7, and 9 weeks of age.

Results: The latency of the JOR was significantly longer and the peak-to-peak amplitude was significantly smaller in the experimental group than in the control group at each age, while the duration was not significantly different. Intragroup comparison of the latency, peak-to-peak amplitude, and duration at 5, 7, and 9 weeks of age revealed no significant differences in either the control or experimental groups.

Conclusions: Unilateral nasal obstruction during growth may have significant effects on maturation of craniofacial function.