Ventilatory roll off during sustained hypercapnia is gender specific in pekin ducks

Abstract

The objective of the present study was to examine the relative roles of peripheral versus central mechanisms in producing ventilatory adjustments in pekin ducks during prolonged (5 h) hypercapnia (5% inspired CO 2 ), and to determine whether these adjustments differed between male and female ducks. After 20 min of CO 2 exposure, intact ducks increased total ventilation (V E ) 2.5-3-fold above control values, due to large increases (∼200%) in tidal volume (V T ) and slightly smaller increases (∼140%) in breathing frequency (f R ). This response was accompanied by respiratory acidosis (pHa fell from ∼7.46 to ∼7.41) and hypercapnia (Pa CO 2 increased from ∼35 to ∼40 Torr). In males,V E fell progressively thereafter due exclusively to a fall in f R , in parallel with a rapid partial recovery of pH (to 7.44) while Pa CO 2 continued to climb (to ∼42 Torr). In females,V E remained elevated during hypercapnia, and no pH recovery occurred. This suggests that a respiratory decline resulting from acid-base compensation (probably due to HCO 3 − mobilization) occurred in males but not in females. Bicarbonate mobilization, and thus pH compensation, may have been reduced in females due to the CaCO 3 requirements of eggshell formation. In males, the acute ventilatory response was reduced slightly by denervation of the carotid bodies or intrapulmonary chemoreceptors, but there was no effect of denervation of either receptor group on the responses to prolonged CO 2 . We conclude that pH compensation triggered by constant or increasing Pa CO 2 , acting at central chemoreceptors, likely mediates the respiratory adjustments seen in male pekin ducks during hypercapnia. Furthermore, we suggest that this ventilatory response be considered a gender-specific hypercapnic ventilatory roll off, in the context of the various time domains of the hypercapnic ventilatory response.

Ventilation changes associated with hatching and maturation of an endothermic phenotype in the Pekin duck,Anas platyrhynchos domestica

“…This large contribution of V T in the chicken compared with the Pekin duck may be due to the higher resting ƒ in the chicken when compared with the duck. Hatchling ventilation responses to hypercapnia are similar to those observed in the adult Pekin duck (5).…”

“…Pekin duck hatchling ƒ is 31, 27, and 47% lower than wedge-tailed shearwater, Muscovy duck, and chicken hatchlings (16,33). At rest, hatchlings breathe at a rate of 33 breaths/min, which is roughly three times the breathing frequency of adult Pekin ducks (2,5,12). A similar difference between hatchling and adult ƒ is observed in chicken and Muscovy ducks (10,12,16).…”

Control of breathing and adaptation to high altitude in the bar-headed goose

“…Body plethysmography was used to measure ventilation, as previously described (13,14). Briefly, the plethysmograph consisted of two parts, a body compartment and a head compartment, separated from each other by a flexible latex collar.…”

Body temperature depression and peripheral heat loss accompany the metabolic and ventilatory responses to hypoxia in low and high altitude birds

“…Body plethysmography was used to measure breathing, as described previously (Dodd and Milsom, 1987;Dodd et al, 2007;Scott and Milsom, 2007). The plethysmograph consisted of two parts, a body compartment and a head compartment, separated from each other by a flexible latex collar.…”