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

Abstract

SUMMARY1. 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 shamoperated ducks, was abolished.2. 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 pHa. 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 of 225 21-2 0. S. BAMFORD AND D. R. JONES asphyxia. Cardio-acceleration and hypertension accompanied each inspiratory burst. The increase in heart rate was 43-9+3-2% of the maximum possible change which could have occurred (i.e. maximum rate in that duck minus the pre-burst rate). Increases in heart rate usually preceded those in blood pressure although only the former were abolished by bilateral vagotomy.5. It is concluded that denervation of the lungs has no obvious effect on the initiation of the cardiovascular responses to diving. Termination of these responses can be achieved either by feed-back from pulmonary receptors or 'central irradiation' of impulses from respiratory to cardiovascular controlling neurones.

The initiation and maintenance of bradycardia in a diving mammal, the muskrat, Ondatra zibethica.

“…Furthermore, it is claimed that nasal receptor input enhances the depressor effects of the arterial chemoreceptors (Angell-James & Daly, 1973;Str0mme & Blix, 1976;Elsner et al 1977). Input from lung receptors or the activities of central respiratory neurones are seen as having a modifying effect on these responses in that they no longer stimulate the cardiovascular system and therefore allow full expression of depressor chemoreceptor and nasal reflexes (Anrep, Pascual & Rdssler, 1936a, b;Daly & Scott, 1958;Daly & Hazzledine, 1963; Angell-James & Daly, 1973;Bamford & Jones, 1976;Lopes & Palmer, 1976; Angell-James & . The role of arterial mechanoreceptors in effecting diving bradycardia in birds and mammals is controversial.…”

The effect of age and the influence of the relative size of the heart, brain, and blood oxygen store on the responses to submersion in mallard ducklings

“…This phenomenon was also noted by Rey (1971) who found that in domestic ducks ranging in age from 1 to 5 months, the younger animals reached their stable bradycardic heart rate faster than those in the older groups. This implies either that the input from nasal and glottal receptors sensitive to water, causing bradycardia (Bamford and Jones 1974;Blix et al 1975), or the cessation of rhythmic input from pulmonary receptors (Bamford and Jones 1976) is more effective in reducing the heart rate in very young ducklings than in older animals. I attempted to differentiate between the two mechanisms by imgating the trachea in artificially ventilated 1-week-old ducklings, but was unable to prevent collapse of the fragile tracheal walls during the subatmospheric phase of the ventilatory cycle.…”

Forced and voluntary diving in ducks: cardiovascular adjustments and their control

“…7;Butler and Woakes 1976). Since cardiorespiratory interactions are well established in dabbling ducks (Bamford and Jones 1976) and also seem to hold for divers (Fig. lo), it is tempting to invoke these interactions to explain cardiac responses in voluntary dives.…”