Postnatal development of right atrial injection of capsaicin-induced apneic response in rats.
Apnea and respiratory failure often occur in infants with pulmonary disease. Bronchopulmonary C-fiber (PCF)-mediated apnea is an important component of respiratory dysfunction. This study was undertaken to define the postnatal development of PCF-mediated apnea. The experiments were conducted in five groups of anesthetized, tracheotomized, and spontaneously breathing rats with ages at postnatal days P1-3, P7-9, P14-16, P21-23, and P56-58. Right atrial bolus injection of three doses of capsaicin (Cap), equivalent to 2, 4, and 8 microg/kg used previously in 450-g rats, was applied to stimulate PCFs. We found that 1) Cap-induced apneic response [percent change from the baseline expiratory duration (Te) values (deltaTe%)] and the sensitivity of this response (deltaTe%.microg(-1)) were significantly greater in the rats <P10 than those >P10; 2) the Cap-induced apneas were vagally dependent in all rats tested; and 3) bivagotomy-induced prolongation of Te was much greater in the rats <P10 than those >P10. From these findings we concluded that, compared with the older rats (>P10), the newborn rats have a stronger PCF-mediated respiratory inhibition that may contribute to infants' vulnerability to respiratory failure.
Pathophysiology Program, Lovelace Respiratory Research Institute, 2425 Ridgecrest Dr. SE, Albuquerque, New Mexico 87108, USA.
Rurong
R
Wang
Fadi
F
Xu
D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001049:Apnea / Q000139:chemically induced* / Q000503:physiopathology*; D002211:Capsaicin / Q000008:administration & dosage / Q000494:pharmacology*; D045853:Exhalation / Q000502:physiology; D006325:Heart Atria / Q000187:drug effects / Q000503:physiopathology; D007267:Injections; D008176:Lung Volume Measurements; D008297:Male; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012143:Respiratory Physiological Phenomena / Q000187:drug effects*; D012137:Respiratory System / Q000187:drug effects / Q000254:growth & development / Q000294:innervation / Q000503:physiopathology; D013997:Time Factors; D014630:Vagus Nerve / Q000503:physiopathology / Q000601:surgery
D002211:Capsaicin