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 Prostaglandi n E-2 (PCE2). The present study was carried out to determine whether PCE2 e nhances the stimulatory effects of chemical stimulants and lung inflation o n vagal pulmonary C fibers, and if so, whether the excitabilities of other types of lung afferents are also augmented by PCE2. In anesthetized, open-c hest rats, administration of PCE2 (1.5 mu g/kg/min for 2 min) did not signi ficantly change the baseline activity of vagal pulmonary C fibers, but it m arkedly enhanced the stimulatory effects of both low (0.25 mu g/kg) and hig h doses (0.5 mu g/kg) of capsaicin on these fibers. Similarly, potentiating effects of PGE(2) were found on the pulmonary C-fiber responses to injecti ons of lactic acid and adenosine, although considerable variability existed in the degrees of potentiation between the different stimulants. Furthermo re, PGE(2) infusion also significantly enhanced the C-fiber response to con stant-pressure lung inflation (tracheal pressure [Pt] = 30 cm H2O). In cont rast, PGE(2) did not alter the responses of either slowly adapting pulmonar y receptors or rapidly adapting pulmonary receptors to lung inflation. In s ummary, these results show that the sensitivity of pulmonary C-fiber affere nts to both mechanical and chemical stimuli is enhanced by PGE(2), suggesti ng that endogenous release of this autocoid may play a part in the airway i rritation and dyspneic sensation associated with airway inflammation.