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Postnatal development of right atrial injection of capsaicin-induced apneic response in rats
1Pathophysiology Program, Lovelace Respiratory Research Institute, 2425 Ridgecrest Dr. SE, Albuquerque, New Mexico 87108, USA.
Insights
Newborn rats exhibit stronger bronchopulmonary C-fiber (PCF)-mediated respiratory inhibition than older rats. This heightened response in early life may increase infants
Area of Science:
- Respiratory Physiology
- Neonatal Medicine
- Neuroscience
Background:
- Infants with pulmonary disease frequently experience apnea and respiratory failure.
- Bronchopulmonary C-fiber (PCF)-mediated apnea is a significant factor in respiratory dysfunction.
- Understanding the postnatal development of PCF-mediated apnea is crucial for infant respiratory health.
Purpose of the Study:
- To define the postnatal developmental trajectory of PCF-mediated apnea.
- To investigate the role of the vagus nerve in PCF-mediated apnea.
- To compare respiratory responses in newborn versus older rats.
Main Methods:
- Experiments were conducted on five groups of anesthetized, tracheotomized, spontaneously breathing rats at different postnatal ages (P1-3, P7-9, P14-16, P21-23, P56-58).
- Capsaicin (Cap) was administered via right atrial bolus injection at three doses to stimulate PCFs.
- Apneic responses (deltaTe%) and sensitivity (deltaTe%.microg(-1)) were measured, along with the effects of bivagotomy on expiratory duration (Te).
Main Results:
- Cap-induced apneic response and sensitivity were significantly higher in rats younger than P10 compared to older rats (>P10).
- Capsaicin-induced apneas were dependent on vagal nerve activity in all tested rats.
- Bivagotomy resulted in a more pronounced prolongation of expiratory duration (Te) in rats younger than P10 than in older rats.
Conclusions:
- Newborn rats (
- This enhanced inhibitory response in neonates may contribute to their vulnerability to respiratory failure.
- The findings highlight the critical role of PCF-mediated reflexes in neonatal respiratory control and dysfunction.
Abstract:
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
