Effects of lung congestion and oleic acid injury on the Hering-Breuer reflex.
Breathing and the Hering-Breuer (HB) reflex may be stimulated by congestion and by acute lung injury, but there is disagreement about the effects of both stimuli. This study evaluated these effects using greater stimulus isolation and control of secondary interactions than have previously been employed. Pressurization of lung vessels and left heart and oleic acid injury were individually imposed on anesthetized open-chest dogs perfused with an external pump and gas exchanger. Lungs were inflated in steps before and during those stimuli. The HB reflex was evaluated from graphs of breathing frequency (fr) vs. airway pressure. Congestion itself had no significant sustained effect on fr, but it slightly depressed the HB reflex. Oleic acid tachypnea that was depressed to pretreatment fr by inflation, implying enhancement of the HB response. Capsaicin and oleic acid had similar effects. Vagal cooling to 8 degrees C slightly depressed the effects of oleic acid and capsaicin, had no effect on the sustained fr response to congestion, and reversed the inhibitory effect of inflation. A stimulation of breathing or an enhancement of the HB reflex by congestion was not confirmed, but oleic acid increased fr and the HB reflex.
Lloyd
T C
TC
Department of Medicine, Indiana University Medical Center, Indianapolis 46223.
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D004285:Dogs; D008168:Lung / Q000187:drug effects* / Q000503:physiopathology; D008297:Male; D019301:Oleic Acid; D009829:Oleic Acids / Q000494:pharmacology*; D011652:Pulmonary Circulation; D012018:Reflex / Q000502:physiology*; D012119:Respiration
D009829:Oleic Acids; D019301:Oleic Acid; D002211:Capsaicin