Pulmonary congestion enhances responses of lung rapidly adapting receptors to cigarette smoke in rabbit.

Abstract

We examined the effects of low-nicotine cigarette smoke, pulmonary venous congestion, and their combination on the activity of rapidly (RAR) and slowly adapting receptors (SAR) in anesthetized rabbits. Pulmonary venous congestion was achieved by inflating a balloon in the left atrium to increase left atrial pressure. We examined smoke effects on RARs (averaged over 15 breaths) at baseline left atrial pressure and at subthreshold and suprathreshold increases in left atrial pressure. At baseline, smoke significantly increased RAR activity from 12.1 +/- 4.2 to 16.2 +/- 4.2 impulses/breath (P < 0.05). At subthreshold increases in left atrial pressure (2.9 +/- 0.6 mmHg), smoke produced larger increases in RAR activity (12.3 +/- 3.3 to 22.5 +/- 4.1 impulses/breath; P < 0.05). Suprathreshold increases in left atrial pressure (9.2 +/- 1.1 mmHg) alone increased RAR activity from 10.9 +/- 3.2 to 19.8 +/- 5.9 impulses/breath (P < 0.05). Smoke had no additional effect (22.3 +/- 4.8 impulses/breath; P > 0.05). There was, however, a transient increase in RAR activity (1st 3 breaths of smoke) under all three conditions. Of nine SARs examined, only two were stimulated by smoke. We conclude that in the rabbit smoke-induced stimulation of RARs is augmented by mild pulmonary venous congestion. of RARs is augmented by mild pulmonary venous congestion.