Vagal stimulation induces increased pulmonary vascular permeability in guinea pig

The effects of vagal stimulation on pulmonary vascular permeability were studied in guinea pigs in vivo using 1251-labeled albumin as a marker of plasma extravasation. Bilateral vagus nerve stimulation (NS) significantly increased the plasma leakage index in both parenchyma and tracheobronchial tissues. The NS-induced plasma leakage in the parenchyma was unaffected by the u-adrenoceptor antagonist phen­ tolamine, the muscarinic receptor antagonist atropine, the ganglionic blocker hexamethonium, or pretreat­ ment with 6-hydroxydopamine or capsaicin, but it was significantly potentiated by the [3-adrenoceptor an­ tagonist propranolol. NS-induced tracheobronchial vascular leakage was markedly inhibited by pretreatment with atropine, hexamethonium, or capsaicin, although it was unaffected by pretreatment with phentola­ mine, propranolol, or 6-hydroxydopamine. By itself, NG-nitro L-arginine methyl ester (L-NAME), an inhibi­ tor of nitric oxide (NO) synthase, had no effect on pulmonary vascular leakage, but it significantly enhanced the NS-induced plasma leakage to parenchyma in a dose-related and L-arginine-reversible manner. Eleva­ tion of blood pressure to a similar extent as that induced by L-NAME by a phenylephrine infusion had no significant effect on the increased plasma leakage induced by NS. These results suggest that vagal stimu­ lation increases plasma extravasation in lung parenchyma through the release of unidentified transmit­ ter(s) in a process that is modulated by endogenous NO and catecholamines (via activation of [3-adreno­ ceptors), and that different mechanisms are involved in the vagally induced plasma extravasation in the pulmonary and tracheobronchial vascular beds. Liu S, Kuo H-P, Sheppard MN, Barnes PJ, Evans TW. Vagal stimulation induces increased pulmonary vascular permeability in guinea pig. Am J Respir Crit Care Med 1994;149:744-50.