Journal of Dental Research, Vol 73, 1797-1802, Copyright © 1994 by International & American Associations for Dental Research Online Journals
Axon reflex vasodilatation in cat dental pulp elicited by noxious stimulation of the gingiva
T. Sasano, S. Kuriwada, N. Shoji, D. Sanjo, H. Izumi and K. Karita
Department of Oral Diagnosis, Tohoku University School of Dentistry, Sendai, Japan.
Antidromic stimulation of sensory nerves has been shown to increase blood
flow in the tissue they innervate. This study was designed to determine if
antidromic vasomotor responses occur in feline dental pulp and if they are
mediated by branched axons supplying both tooth pulp and gingiva. Dynamic
changes in pulpal blood flow (PBF) elicited by electrical stimulation,
pinching, heating, and capsaicin application to the gingivae were
investigated in cat mandibular canine teeth by means of Laser Doppler
Velocimetry. All inferior alveolar nerve bundles and the cervical
sympathetic trunk had been previously sectioned to avoid the occurrence of
brainstem reflexes, e.g., somato-autonomic vasomotor reflexes. Increases in
PBF were observed in seven out of 12 cats when a restricted gingival area
adjacent to the canine teeth was stimulated as described, but the increases
were abolished after the sensitive gingival area was painted with lidocaine
jelly, a surface anesthetic. These vasodilator responses, remarkably
reduced following repeated application of 30 mM of capsaicin, are
considered to be induced via antidromic activation of capsaicin-sensitive
nociceptive nerve fibers, presumably by axon reflex mechanisms, suggesting
that nerve terminals supplying the gingiva originate from parent axons
which have collaterals that innervate the canine tooth pulp.
