Sensitization of nociceptive c-fibers in zinc-deficient rats.
Izumi, Hiroshi, Hiroshi Mori, Taro Uchiyama, Shoko Kuwazuru, Yuuki
Ozima, Ikuko Nakamura, and Shigeru Taguchi.
Department of Physiology, Tohoku University School of Dentistry,
Sendai, Japan, Pharmacology Research Division, Pharmaceutical
Research Laboratories, Shiseido Research Center, Yokohama, Department
of Hospital Pharmacy, Institute of Development, Aging and Cancer,
Tohoku University School of Dentistry, Sendai, Japan
APStracts 2:0028R, 1995.
A marked decrease in zinc concentration was observed in plasma (P <
0.001), in hindpaw skin (P < 0.01), and in dorsal skin (P < 0.01) in
zinc-deficient rats (rats fed a zinc-deficient chow for 3 weeks),
compared to the control rats who had been fed the same zinc-deficient
chow supplemented with ZnCO3 (50 mg kg-1 chow). The threshold
intensity needed to elicit vasodilatation in the hindpaw skin of the
zinc-deficient rats on electrical stimulation of the saphenous nerve
in a peripheral direction was markedly lower (P < 0.01) than that in
the control rats. No difference was observed between control (n = 5)
and zinc-deficient rats (n = 5) in the magnitude of the plasma
extravasation evoked by either histamine or substance P. There was no
difference between control and zinc-deficient rats in terms of the
dose-response curve for the release of histamine by substance P. PGE2
concentration in the hindpaw skin of the zinc-deficient rats was
nearly 4-fold higher (P < 0.01) than that of the control rats, while
no difference in the LTB4 level in the hindpaw skin was observed
between control and zinc-deficient rats. From the present study, it
seems likely that an increased level of PGE2 in the vicinity of the
nociceptive C-fiber terminals in the hindpaw skin of zinc-deficient
rats may sensitize the terminals of the nociceptive C-fibers of the
saphenous afferent nerve in the hindpaw and thus facilitate the
production of antidromic vasodilatation.
ELECTRICAL STIMULATION of sensory afferent nerves, such as the
saphenous and inferior alveolar nerves, in a peripheral direction
elicits vasodilatation and plasma extravasation in the area of skin
and lip from which their sensory nerve fibers originate (4, 14, 16
-18). These phenomena are thought to be mediated via activation of
nociceptive C-fibers running in the sensory afferent nerves and via
activation of mast cells and are termed "antidromic vasodilatation"
and "antidromic plasma extravasation", respectively.
Received 13 October 1994; accepted in final form 3 January 1995.
APS Manuscript Number R594-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 February 1995.