Murine airway slowly‐adapting receptor responses to lung inflation: a role for serotonin? (879.19)

Abstract

The mechanical phenotype of murine airway slowly‐adapting receptors (SARs), which are mechanosensitive afferents physiologically characterized by maintained discharge to sustained transmural pressure, is only partially defined. Adriaensen et al. suggest that densely‐innervated pulmonary neuroepithelial bodies (NEBs) are a morphological equivalent of SARs (Adriaensen et al. 2006, J Appl Physiol). Since NEBs release serotonin (5‐HT) in response to stretch in vitro (Pan et al. 2006, Am J Physiol Lung Cell Mol Biol), we characterized the mechanosensitivity of SARs during quasi‐static inflation to 20 cmH2O in male C57BL/6 mice and tested the impact of 5‐HT3 receptor blockade (i.v. tropisetron, Trop; 4.5mg/kg). SAR (n=8) discharge frequency (f; impulses/s) mechanosensitivity was proportional to tracheal pressure. Trop caused a small (3‐8%) but significant decrease in f vs. control (P=0.005; 2‐way ANOVA‐RM; mean±SEM (imp/s): 5cmH2O ‐ con: 91±13, Trop: 87±13; 10cmH2O ‐ con: 153±25, Trop: 143±22; 15cmH2O ‐ con: 192±29, Trop: 180±28; 20cmH2O ‐ con: 176±14, Trop: 164±15). It remains to be seen whether such a modest reduction in SAR discharge has a physiologic impact on the reflex effects of SAR medullary input.Grant Funding Source: Supported by: CIHR (JTF; MOP81211) & NSERC PostGrad Scholarship (NJD)