Inhibitory activity of the novel CB2 receptor agonist, GW833972A, on guinea-pig and human sensory nerve function in the airways.
OBJECTIVE
Sensory nerves regulate central and local reflexes such as airway plasma protein leakage, bronchoconstriction and cough. Sensory nerve activity may be enhanced during inflammation such that these protective effects become exacerbated and deleterious. Cannabinoids are known to inhibit airway sensory nerve function. However, there is still controversy surrounding which receptor is involved in eliciting these effects.


METHODS
We have adopted a pharmacological approach, including using a novel, more selective CB(2) receptor agonist, GW 833972A (1000-fold selective CB(2)/CB(1)), and receptor selective antagonists to investigate the inhibitory activity of cannabinoids on sensory nerve activity in vitro and in vivo in guinea-pig models of cough and plasma extravasation.


RESULTS
GW 833972A inhibited capsaicin-induced depolarization of the human and guinea-pig and prostaglandin E(2) (PGE(2)) and hypertonic saline-induced depolarization of the guinea-pig isolated vagus nerve in vitro. GW 833972A also inhibited citric acid-induced cough but not plasma extravasation in the guinea-pig and this effect was blocked by a CB(2) receptor antagonist.


CONCLUSIONS
This confirms and extends previous studies highlighting the role of CB(2) receptors in the modulation of sensory nerve activity elicited both by the exogenous ligands capsaicin and hypertonic saline but also by endogenous modulators such as PGE(2) and low pH stimuli. These data establish the CB(2) receptor as an interesting target for the treatment of chronic cough.
Belvisi
M G
MG
Respiratory Pharmacology Group, Airway Disease Section, National Heart and Lung Institute, Faculty of Medicine, Imperial College London, London, UK. m.belvisi@imperial.ac.uk
Patel
H J
HJ
Freund-Michel
V
V
Hele
D J
DJ
Crispino
N
N
Birrell
M A
MA
D000328:Adult; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D019343:Citric Acid; D003371:Cough / Q000188:drug therapy* / Q000503:physiopathology; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D008297:Male; D008875:Middle Aged; D009475:Neurons, Afferent / Q000187:drug effects* / Q000378:metabolism; D010949:Plasma / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D043885:Receptor, Cannabinoid, CB2 / Q000819:agonists* / Q000037:antagonists & inhibitors / Q000378:metabolism; D012462:Saline Solution, Hypertonic / Q000494:pharmacology
C533061:GW833972A; D011725:Pyridines; D011743:Pyrimidines; D043885:Receptor, Cannabinoid, CB2; D012462:Saline Solution, Hypertonic; D019343:Citric Acid; D002211:Capsaicin