Prostaglandin E(2) enhances chemical and mechanical sensitivities of pulmonary C fibers in the rat.
It has been recently reported that pulmonary reflex responses to injection or inhalation challenge of capsaicin are enhanced by exogenous Prostaglandin E(2) (PGE(2)). The present study was carried out to determine whether PGE(2) enhances the stimulatory effects of chemical stimulants and lung inflation on vagal pulmonary C fibers, and if so, whether the excitabilities of other types of lung afferents are also augmented by PGE(2). In anesthetized, open-chest rats, administration of PGE(2) (1.5 microgram/kg/min for 2 min) did not significantly change the baseline activity of vagal pulmonary C fibers, but it markedly enhanced the stimulatory effects of both low (0.25 microgram/kg) and high doses (0.5 microgram/kg) of capsaicin on these fibers. Similarly, potentiating effects of PGE(2) were found on the pulmonary C-fiber responses to injections of lactic acid and adenosine, although considerable variability existed in the degrees of potentiation between the different stimulants. Furthermore, PGE(2) infusion also significantly enhanced the C-fiber response to constant-pressure lung inflation (tracheal pressure [Pt] = 30 cm H(2)O). In contrast, PGE(2) did not alter the responses of either slowly adapting pulmonary receptors or rapidly adapting pulmonary receptors to lung inflation. In summary, these results show that the sensitivity of pulmonary C-fiber afferents to both mechanical and chemical stimuli is enhanced by PGE(2), suggesting that endogenous release of this autocoid may play a part in the airway irritation and dyspneic sensation associated with airway inflammation.
Department of Physiology, University of Kentucky, Lexington, Kentucky, USA.
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D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects / Q000294:innervation* / Q000502:physiology; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014630:Vagus Nerve / Q000187:drug effects*
D015232:Dinoprostone; D002211:Capsaicin