Journal of Applied Physiology, Vol 73, Issue 4 1402-1412, Copyright © 1992 by American Physiological Society

ARTICLES

Effect of bilateral vagotomy on oxygenation, arousal, and breathing movements in fetal sheep

S. U. Hasan and A. Rigaux
Department of Paediatrics, University of Calgary, Alberta, Canada.

To investigate the effects of bilateral cervical vagotomy on arousal and breathing responses, we studied eight sham-operated and eight chronically instrumented unanesthetized vagotomized sheep fetuses between 136 and 144 days of gestation (term approximately 147 days). Each fetus was instrumented to record sleep states, diaphragmatic electromyogram, blood pressure, pH, and blood gas tensions. In a randomized order, fetal lungs were distended with four different O2 concentrations: 0 (100% N2), 21, 50, and 100% at a continuous positive airway pressure of 30 cmH2O via an in situ Y-endotracheal tube. Under control conditions, inspiratory time and the duration of the single longest breathing episode decreased from 598 +/- 99 (SD) ms and 24 +/- 10 min in sham group to 393 +/- 162 ms and 11.0 +/- 3.0 min in vagotomized group (P = 0.04 and 0.033), respectively. In response to lung distension with 100% N2, breathing time decreased from 44 +/- 17 to 20 +/- 18% (P = 0.045) in sham-operated fetuses, whereas it remained unchanged in the vagotomized group. In response to 100% O2, fetal arterial PO2 increased in five of eight fetuses sham-operated from 18.2 +/- 5.1 to 227 +/- 45 Torr (P = 0.0001) and in six of eight vagotomized fetuses from 18.5 +/- 4.4 to 172 +/- 39 Torr (P < 0.001). Although arousal was observed in all oxygenated fetuses at the onset of breathing, the duration of arousal was markedly attenuated in vagotomized fetuses (14 +/- 10 vs. 46 +/- 29 min in sham group; P = 0.024). Frequency and amplitude of breathing and respiratory output (frequency x amplitude) increased only in sham group (P = 0.02, 0.004, and 0.0002, respectively). We conclude that in response to lung distension and oxygenation, arousal and stimulation of breathing during active and quite sleep are critically dependent on intact vagal nerves.

This article has been cited by other articles:

				R. Wang and F. Xu Postnatal development of right atrial injection of capsaicin-induced apneic response in rats J Appl Physiol, July 1, 2006; 101(1): 60 - 67. [Abstract] [Full Text] [PDF]

				S. Lalani, J. E. Remmers, Y. MacKinnon, G. T. Ford, and S. U. Hasan Hypoxemia and low Crs in vagally denervated lambs result from reduced lung volume and not pulmonary edema J Appl Physiol, August 1, 2002; 93(2): 601 - 610. [Abstract] [Full Text] [PDF]

				S. Lalani, J. E. Remmers, F. H. Green, A. Bukhari, G. T. Ford, and S. U. Hasan Effects of vagal denervation on cardiorespiratory and behavioral responses in the newborn lamb J Appl Physiol, November 1, 2001; 91(5): 2301 - 2313. [Abstract] [Full Text] [PDF]

				K. A. Wong, A. Bano, A. Rigaux, B. Wang, B. Bharadwaj, S. Schurch, F. Green, J. E. Remmers, and S. U. Hasan Pulmonary vagal innervation is required to establish adequate alveolar ventilation in the newborn lamb J Appl Physiol, September 1, 1998; 85(3): 849 - 859. [Abstract] [Full Text] [PDF]