title: Alteration of primary afferent activity following inferior alveolar nerve transection in rats.
abstract: BACKGROUND
  In order to evaluate the neural mechanisms underlying the abnormal facial pain that may develop following regeneration of the injured inferior alveolar nerve (IAN), the properties of the IAN innervated in the mental region were analyzed.
  
  
  RESULTS
  Fluorogold (FG) injection into the mental region 14 days after IAN transection showed massive labeling of trigeminal ganglion (TG). The escape threshold to mechanical stimulation of the mental skin was significantly lower (i.e. mechanical allodynia) at 11-14 days after IAN transection than before surgery. The background activity, mechanically evoked responses and afterdischarges of IAN Adelta-fibers were significantly higher in IAN-transected rats than naive. The small/medium diameter TG neurons showed an increase in both tetrodotoxin (TTX)-resistant (TTX-R) and -sensitive (TTX-S) sodium currents (INa) and decrease in total potassium current, transient current (IA) and sustained current (IK) in IAN-transected rats. The amplitude, overshoot amplitude and number of action potentials evoked by the depolarizing pulses after 1 muM TTX administration in TG neurons were significantly higher, whereas the threshold current to elicit spikes was smaller in IAN-transected rats than naive. Resting membrane potential was significantly smaller in IAN-transected rats than that of naive.
  
  
  CONCLUSIONS
  These data suggest that the increase in both TTX-S INa and TTX-R INa and the decrease in IA and Ik in small/medium TG neurons in IAN-transected rats are involved in the activation of spike generation, resulting in hyperexcitability of Adelta-IAN fibers innervating the mental region after IAN transection.
authors.affiliation: Department of Dysphagia Rehabilitation, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan.
authors.forename: Kazuharu
authors.initials: K
authors.lastname: Nakagawa
authors.forename: Mamoru
authors.initials: M
authors.lastname: Takeda
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Tsuboi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kondo
authors.forename: Junichi
authors.initials: J
authors.lastname: Kitagawa
authors.forename: Shigeji
authors.initials: S
authors.lastname: Matsumoto
authors.forename: Azusa
authors.initials: A
authors.lastname: Kobayashi
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Sessle
authors.forename: Masamichi
authors.initials: M
authors.lastname: Shinoda
authors.forename: Koichi
authors.initials: K
authors.lastname: Iwata
mesh_terms: D000200:Action Potentials; D000818:Animals; D008340:Mandibular Nerve / Q000502:physiology; D008564:Membrane Potentials; D009475:Neurons, Afferent / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D061221:Trigeminal Nerve Injuries