PULMONARY CONGESTION ENHANCES RESPONSES OF LUNG RAPIDLY ADAPTING RECEPTORS TO CIGARETTE-SMOKE IN RABBIT

We examined the effects of low-nicotine cigarette smoke, pulmonary ven ous congestion, and their combination on the activity of rapidly (RAR) and slowly adapting receptors (SAR) in anesthetized rabbits. Pulmonar y venous congestion was achieved by inflating a balloon in the left at rium to increase left atrial pressure. We examined smoke effects on RA Rs (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 inc reases 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 incre ase in RAR activity (1st 3 breaths of smoke) under all three condition s. Of nine SARs examined, only two were stimulated by smoke. We conclu de that in the rabbit smoke-induced stimulation of RARs is augmented b y mild pulmonary venous congestion.