Subtypes of nociceptive units in the rat temporomandibular joint.
Response properties of nociceptors in the rat's temporomandibular joint (TMJ) were investigated using an in vitro TMJ-nerve preparation. Recordings were obtained from 33 nociceptive units that responded to mechanical, chemical, and/or thermal stimuli. According to both characteristics of nociceptors and afferent fibers, nociceptive units in the TMJ area were classified into the following four subtypes: Adelta-high-threshold mechanonociceptor (HTM) (12.1%), Adelta-polymodal nociceptor (POLY) (36.4%), C-HTM (12.1%), and C-POLY (39.4%). The mean mechanical threshold of the Adelta units was significantly lower than that of the C units. Bradykinin increased the discharge of Adelta- and C-POLY units. No significant differences of thermal thresholds between Adelta and C units were found. The percentage of Adelta units was 47.2% and of C units was 52.8%, respectively. In the TMJ area, POLY units were predominant (75.8%), suggesting that inflammatory reactions can easily evoke pain sensation.
D000818:Animals; D008297:Male; D009619:Nociceptors / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D012684:Sensory Thresholds / Q000502:physiology*; D013704:Temporomandibular Joint / Q000502:physiology*