Is the Supratrigeminal Area Involved in Jaw-Opening Reflex Activity?
Stimulation of the inferior alveolar nerve (IAN) elicits the so-called jaw-opening reflex (JOR) which is associated with excitation of the jaw-opening muscles and inhibition of the jaw-elevator muscles. High threshold afferents with their cell bodies located in the trigeminal ganglion (tg) are responsible for the activation of the jaw-opening muscles, whereas low threshold afferents with their cell bodies in the mesencephalic trigeminal nucleus (Me5) are involved in the inhibition of the jaw-elevator muscles (Dessem, Iyadurai & Taylor, 1988). The central neuronal routing of the JOR is not fully understood yet. High threshold short latency JOR activity is mediated through a disynaptic pathway involving interneurones in the trigeminal brainstem nuclear complex (TBNC). However, the location of interneurones involved in high-threshold long latency JOR activity is still disputed. This study indicates that the supratrigeminal area (Su5), adjacent to the Me5, contains elements of a neuronal pathway involved in reflex activation of the jaw-opening muscles.
KeywordsTrigeminal Ganglion Reflex Activity Inferior Alveolar Nerve Digastric Muscle High Stimulus Frequency
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