AJP - Regulatory, Integrative and Comparative Physiology, Vol 265, Issue 4 733-R738, Copyright © 1993 by American Physiological Society
Reflex vasodilatation in the cat lip elicited by stimulation of nasal mucosa by chemical irritants
H. Izumi and K. Karita
Department of Physiology, Tohoku University School of Dentistry, Sendai, Japan.
Local application of capsaicin (threshold dose 150 microM) or nicotine
(threshold dose 15 mM) to the nasal mucosa as well as electrical
stimulation (threshold intensity 10 V) of the nasal mucosa elicited dose-
or intensity-dependent blood flow increases in the ipsilateral lower lips
of the anesthetized cats. Pretreatment with 3 mM capsaicin applied locally
to the nasal mucosa abolished or reduced the vasodilation in response to
capsaicin, nicotine, and ammonia vapor but not to light mechanical or
electrical stimulation of the nasal mucosa. The blood flow increases
elicited by all above stimuli were greatly reduced by pretreatment with
hexamethonium, an autonomic ganglion blocker. These results suggest that
stimulation of the nasal mucosa by chemical (capsaicin, nicotine, ammonia),
mechanical, or electrical methods elicits the autonomic reflex
vasodilatation in the cat lower lips. Furthermore, there seem to be at
least two types of afferent fibers in the nasal mucosa of the cats: one
type is capsaicin-sensitive fibers, while another type is
capsaicin-resistant fibers involved in reflex vasodilatation.
