Airway Deflation Activated Receptors Are Stimulated by Hypertonic Saline

Abstract

Recently, deflation activated receptors (DARs) in the lung have been identified as a group of airway sensory receptors. DARs often share their afferents with rapidly adapting receptors (RARs) as well as slowly adapting pulmonary stretch receptors (SARs) to form a sensory unit. However, the afferent properties of DARs have not been well characterized. It has been reported that airway RAR units are stimulated, whereas typical SAR units (units do not respond to lung deflation) are not stimulated by hypertonic saline. Since RAR units are often share afferents with DARs, possibly, it is the DARs that are stimulated by hypertonic saline. The present study determines whether DARs can be stimulated by increased osmolarity. In anesthetized, open‐chest and artificially ventilated rabbits, we recorded single unit activities from typical SAR units and SAR units that respond to lung deflation (units contain DARs). We examined responses of these two groups to injection of hypertonic saline (8.1% sodium chloride, 0.1 ml) into receptive fields in the lung. Hypertonic saline decreased the activity of typical SARs, although not substantially. At baseline, activity of typical SAR units was 40.3 ± 5.4 imp/s (n=12). It decreased to 34.8 ± 4.7 imp/s (p<0.05) at 17.5 seconds after injection of hypertonic saline. On the other hand, hypertonic saline stimulated deflation activated SAR units significantly. Baseline activity increased from 15.9 ± 2.2 imp/s to its speak of 43.4 ± 10.0 imp/s (n=10, p<0.01) at 10.5 seconds after injection. The activity returned to the control level within a minute. Our results show that behavior of deflation activated and typical SAR units was different. The former, but not the latter, was stimulated by hypertonic saline. We conclude that DARs are stimulated by hypertonic saline.Support or Funding Information(Supported by a VA Merit Review Award PULM‐029‐10S)