PULMONARY VAGAL REFLEXES AND BREATHING PATTERN ARE NOT ALTERED IN ELASTASE-INDUCED EMPHYSEMA IN RATS

The role of nonmyelinated and myelinated vagal afferents in pulmonary reflexes and breathing pattern was examined in elastase-treated emphys emic rats. Fourteen to 17 days after intratracheal instillation of 1 I U/gm of porcine pancreatic elastase or 0.5 mL of saline, elastase-trea ted rats had a decreased alveolar surface area to volume of parenchyma (Sv) (42.44 +/- 1.7 vs. 31.51 +/- 1.1 mm(2)/mm(3)), increased quasist atic compliance (QSC) (1.05 +/- 0.06 vs. 1.25 +/- 0.09 mL/cm H2O), fun ctional residual capacity (FRC) (4.31 +/- 0.10 vs 5.88 +/- 0.37 mL), r esidual volume (RV) (3.02 +/- 0.14 vs 4.27 +/- 0.31 mL), and total lun g capacity (TLC) (14.04 +/- 0.28 vs. 15.58 +/- 0.54 mL). There were no changes in the strength of the pulmonary chemoreflex, the strength of the Hering-Breuer inflation reflex, or breathing pattern before or af ter vagal perineural capsaicin treatment (VPCT) or vagotomy. There wer e, however significant negative correlations between Sv and TLC, FRC a nd RV, and a near significant (p<.09) negative correlation between Sv and QSC, but no significant correlations between Sv and indices of eit her the pulmonary chemoreflex or Hering-Breuer inflation reflex. The r esults indicate that pulmonary vagal nonmyelinated and myelinated refl ex activity and breathing pattern are not affected by elastase-induced emphysema in rats.