Comparison of cough reflex sensitivity after an inhaled antigen challenge between actively and passively sensitized guinea pigs.
BACKGROUND
Late asthmatic response is observed following antigen challenge in actively, but not passively, sensitized guinea pigs. Although cough reflex sensitivity is increased after antigen challenge in actively sensitized guinea pigs, it is unknown whether the antigen-induced increase in cough reflex sensitivity develops in passively sensitized animals. The aim of this study was to compare the cough reflex sensitivity to inhaled capsaicin after an inhaled antigen challenge between actively and passively sensitized guinea pigs.


METHODS
Measurement of number of coughs elicited by increasing concentrations of capsaicin (10(-6) and 10(-4) M) and bronchial responsiveness to ascending concentrations of methacholine, and analysis of bronchoalveolar lavage fluid (BALF) were separately performed 24 h after an antigen challenge in actively and passively sensitized guinea pigs.


RESULTS
Percentage of eosinophils in BALF and bronchial responsiveness to methacholine were increased 24 h after the antigen challenge in both actively and passively sensitized animals compared with saline-challenged actively and passively sensitized animals, respectively. Absolute number of eosinophils in BALF from actively sensitized and antigen-challenged guinea pigs was significantly greater than that from passively sensitized and antigen-challenged animals. Cough response to capsaicin and concentration of substance P in BALF were increased 24 h after the antigen challenge in actively sensitized guinea pigs, but not in passively sensitized guinea pigs. Bronchial responsiveness, cough reflex sensitivity and substance P concentration and total cells in BALF were increased in actively sensitized and saline challenged guinea pigs compared with passively sensitized and saline challenged animals.


CONCLUSIONS
The results suggest that active sensitization per se increases cough reflex sensitivity accompanied by increased inflammatory cells and substance P level in BALF, and antigen challenge further increases them, while simple IgE- and/or IgG-mediated allergic reaction per se or the low intensity of eosinophil infiltration in the airway itself may not affect cough reflex sensitivity in guinea pigs.
Hara
Johsuke
J
Respiratory Medicine, Cellular Transplantation Biology, Kanazawa University Graduate School of Medical Science, Kanazawa City, Ishikawa, 920-8641, Japan. hara@med3.m.kanazawa-u.ac.jp
Fujimura
Masaki
M
Myou
Shigeharu
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Oribe
Yoshitaka
Y
Furusho
Shiho
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Kita
Toshiyuki
T
Katayama
Nobuyuki
N
Abo
Miki
M
Ohkura
Noriyuki
N
Herai
Yoriko
Y
Hori
Akihiro
A
Ishiura
Yoshihisa
Y
Nobata
Kouichi
K
Ogawa
Haruhiko
H
Yasui
Masahide
M
Kasahara
Kazuo
K
Nakao
Shinji
S