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Activation of pulmonary C fibres by adenosine in anaesthetized rats: role of adenosine A 1 receptors
Author(s) -
Hong JuLun,
Ho ChingYin,
Kwong Kevin,
Lee LuYuan
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.109br.x
Subject(s) - stimulation , aminophylline , adenosine receptor , adenosine , medicine , receptor , antagonist , bronchoconstriction , capsaicin , adenosine receptor antagonist , receptor antagonist , anesthesia , adenosine a1 receptor , endocrinology , pharmacology , chemistry , agonist , asthma
1 Intravenous administration of adenosine (Ado) to patients can cause dyspnoea, chest discomfort and bronchoconstriction. To assess the role of vagal pulmonary C fibres in evoking these adverse reactions, the effect of Ado on single pulmonary C fibres was studied in anaesthetized and artificially ventilated rats. 2 Right‐atrial injection of Ado (320 μg kg −1 ) activated 68 % (73/107) of pulmonary C fibres; the total number of action potentials during a period of 15 s increased from a baseline of 0.2 ± 0.1 impulses to a peak of 16.4 ± 2.6 impulses ( P < 0.01, n = 107) after Ado. Inosine, the metabolite of Ado, did not activate any of eleven C fibres tested in six rats. Furthermore, C fibres were activated only by right‐atrial and not by left‐ventricular injection of the same dose of Ado. 3 Unlike the immediate and transient stimulation of C fibres by capsaicin, the C fibre stimulation by Ado had a latency of 6.5 ± 0.3 s (range, 3‐18 s) and lasted longer. 4 The stimulation of C fibres by Ado was significantly attenuated by pretreatment with aminophylline, a non‐selective Ado receptor antagonist, was completely prevented by 1,3‐dipropyl‐8‐cyclopentylxanthine, an Ado A 1 receptor antagonist, but was unaffected by 3,7‐dimethy‐1‐propargylxanthine, an A 2 receptor antagonist. None of these Ado receptor antagonists prevented capsaicin‐induced C fibre stimulation. 5 In conclusion, Ado stimulates pulmonary C fibre terminals through an activation of A 1 receptors. The stimulation of pulmonary C fibres may play an important role in Ado‐induced adverse respiratory effects.