Respiratory and cardiovascular interactions in ducks: the effect of lung denervation on the initation of and recovery from some cardiovascular responses to submergence.

Lung denervation in ducks, by sectioning all vagal branches to one lung following mid-cervical vagotomy on the other side, resulted in immediate bradycardia and fall in breathing frequency. Some 3-5 weeks after lung denervation breathing frequency was within the normal range but the lung inflation reflex, present in unilaterally vagotomized sham-operated ducks, was abolished. During 2 min dives there were no significant differences between sham-operated and denervated ducks in heart rate, arterial blood pressure, blood gas tensions and pH(a). However, during recovery from diving heart rate increased more slowly in denervates and breathing rate was significantly below that attained by shams, although tidal volume rose to a maximum increase of 139% to a maximum of 225% of the pre-dive value in denervates in contrast to a maximum increase of 139% of pre-dive in sham-operated ducks. Both sham-operated and denervated ducks exhibited a significant fall in diastolic blood pressure 60 sec after emergence...