Alteration of the second branch of the trigeminal nerve activity following inferior alveolar nerve transection in rats.
After transection of the inferior alveolar nerve (IAN), the whisker pad area, which is innervated by the infraorbital nerve (ION) that was not injured, showed hypersensitivity to mechanical stimulation. Two days after IAN transection, threshold intensity for escape behavior to mechanical stimulation of the ipsilateral whisker pad area was less than 4.0 g, indicating mechanical allodynia. A total of 68 single fiber discharges were recorded from ION fibers at 3 days after IAN transection. The responses of C- and A-fibers were classified according to their conduction velocity. The C-fiber activities were not affected by IAN transection, whereas A-fiber activities were significantly enhanced by IAN transection as indicated by an increase in background activity and mechanically evoked response. Since the A-fiber responses were significantly affected by IAN transection, patch clamp recording was performed from middle to large diameter retrogradely labeled and acutely dissociated trigeminal ganglion (TRG) neurons. The I(K) (sustained) and I(A) (transient) currents were significantly smaller and hyperpolarization-activated current (I(h)) was significantly larger in TRG neurons of rats with IAN transection as compared to those of naive rats. Furthermore, current injection into TRG neurons induced high frequency spike discharges in rats with IAN transection. These data suggest that changes in K(+) current and I(h) observed in the uninjured TRG neurons reflect an increase in excitability of TRG neurons innervated by the ION after IAN transection, resulting in the development of mechano-allodynia in the area adjacent to the injured IAN innervated region.
Tsuboi
Yoshiyuki
Y
Department of Physiology, School of Dentistry, Nihon University, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan Department of Physiology, School of Dentistry at Tokyo, Nippon Dental University, 1-9-20, Fujimi-cho, Chiyoda-ku, Tokyo 102-8159, Japan Division of Functional Morphology, Dental Research Center, Nihon University School of Dentistry, Tokyo 101-8310, Japan Department of Dysphagia Rehabilitation, Nihon University School of Dentistry, Tokyo 101-8310, Japan Department of Dental Anesthesiology, Nihon University School of Dentistry, Tokyo 101-8310, Japan Department of Biomedical Sciences, University of Maryland Dental School, Baltimore, MD 21201, USA Division of Applied System Neuroscience Advanced Medical Research Center, Nihon University Graduate School of Medical Science, 30-1 Ohyaguchi-Kamimachi Itabashi, Tokyo 173-8610, Japan.
Takeda
Mamoru
M
Tanimoto
Takeshi
T
Ikeda
Mizuho
M
Matsumoto
Shigeji
S
Kitagawa
Junichi
J
Teramoto
Kohei
K
Simizu
Kohei
K
Yamazaki
Yoko
Y
Shima
Asako
A
Ren
Ke
K
Iwata
Koichi
K
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D004924:Escape Reaction / Q000502:physiology; D008297:Male; D008340:Mandibular Nerve / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014276:Trigeminal Nerve / Q000502:physiology*; D061221:Trigeminal Nerve Injuries