Medical Journal of the Islamic Republic Of Iran
مجله پزشکی جمهوری اسلامی ایران
Med J Islam Repub Iran
Medical Sciences
http://mjiri.iums.ac.ir
2
journal2
1016-1430
2251-6840
8
10.18869/mjiri
14
8888
13
en
jalali
1377
8
1
gregorian
1998
11
1
12
3
online
1
fulltext
en
INCREASED HISTAMINE Hi RECEPTOR BLOCKADE BY CHLORPHENIRAMINE IN TRACHEAL CHAINS OF ASTHMATIC GUINEA PIGS
Physiology
Physiology
Original Research: Basic Science in Medicine
Original Research: Basic Science in Medicine
Receptor affinity and drug delivery to the receptor sites could be determinant
factors for the increased bronchial responsiveness seen in asthma. Competitive
antagonism blockade which is measured as dose ratio-l (DR-I) depends only on
these two factors. Therefore, in this study we have examined histamine HI blockade
by chlorpheniramine on isolated tracheal chains of asthmatic compared to control
guinea pigs.
An experimental model of asthma was induced in guinea pigs by injection and
inhalation of ovalbumin (OA), and tracheal chains of asthmatic and control animals
(for each group n= 12) were prepared. The responses of tracheal chains to cumulative
concentrations of histamine (H) in the absence and presence of 5 nM chlorpheniramine
was measured, and the effective concentration of H causing 50% of maximum
response (ECso H) was obtained. The chlorpheniramine blockade (DR-I) was
calculated by (post chlorpheniramine EC50H/EC50 H)-1. The response of tracheal
chains to 0.1 % OA relative to the contraction obtained by 10 mM methacholine was
also measured.
The tracheal response of asthmatic guinea pigs to OA was significantly higher
than that of control animals (mean ± SEM, 57.03±4.99 VS. 3.92±1 .14, p<O.OO l ).
Histamine HI receptor blockade by chlorpheniramine (DR-I) was also significantly
higher in tracheas of asthmatic compared to control animals (1 7 .34±3.8 9vs. 4.1I±I.08,
p<0.01). There was a significant correlation between (DR-I) and tracheal responses
to OA (r= 0.51 ,p<0.05).
This enhanced histamine HI receptor blockade in tracheal chains of asthmatic
animals confirms our previous findings which was predicted to be due to increased
drug delivery to the receptor. Drug delivery could also be a determinant factor for
bronchial responsiveness to most stimulating agents in asthma.
Histamine HI receptors, chlorpheniramine blockade, asthma, bronchial responsiveness
265
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http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-456&slc_lang=en&sid=1
MH
BOSKABADY
20031947532846004788
20031947532846004788
Yes
From the Department of Physiology, Ghaem Medical Center, Mashhad University of Medical Sciences, Mashhad, Islamic Republic of Iran.
M
HARATI
20031947532846004789
20031947532846004789
No