An in vitro temporomandibular joint-nerve preparation for pain study in rats

A novel in vitro TMJ-nerve preparation was developed to quantitatively study peripheral sensory mechanisms of temporomandibular joint (TMJ). The TMJ region on one side (including mandibular head, disc, retrodiscal tissue and mandibular fossa) of adult Wistar albino rats was excised together with the auriculo-temporal nerve. The block was preserved in a modified Krebs-Henseleit solution saturated with O(2)/CO(2) (95/5%) gas mixture. Using a calibrated von Frey type apparatus, mechanical noxious stimulation was applied directly to various sites within the TMJ region. In addition, thermal and chemical noxious stimuli were also attempted. Stable recordings of single unit activities from the auriculo-temporal nerve could be obtained for as long as 5 h, which was sufficient to analyze the response properties of the TMJ units to various stimuli. This new preparation would be useful for investigating TMJ peripheral sensory mechanisms, especially pain, and potentially makes it possible to reveal neural mechanisms of temporomandibular arthralgia, a syndrome that has recently shown an increased incidence in clinical dentistry.