Postnatal Development of Hypoxic and Hypercapnic Ventilatory Responses in Coturnix Quail

Abstract

Newborn mammals generally exhibit a biphasic hypoxic ventilatory response (HVR) in which the initial increase in ventilation is followed by a progressive decline toward (or below) baseline; the magnitude of the secondary decline diminishes with age. Considerably less is known about postnatal development of the HVR in birds, although a recent study did not detect a biphasic HVR in nestling red‐winged blackbirds (Dzialowski et al., Am J Physiol 311:R1105–R1112, 2016). We used head‐body plethysmography to characterize the ventilatory responses of Coturnix quail chicks to 15‐min challenges of 11% O2 or 4% CO2 at 0–1, 3–4, and 6–7 days of age. The magnitude of the HVR increased with postnatal age (21±4, 35±3, and 42±4 % increase from baseline, respectively; mean±SEM, P<0.01). The HVR was biphasic at P0–1 and (to a lesser extent) at P3–4, but not at P6–7. In contrast, the magnitude of the hypercapnic ventilatory response decreased with age (76±8, 54±4, 31±3 % increase from baseline, respectively; P<0.001). The hypercapnic ventilatory response was characterized by a relatively sustained increase in ventilation in all age groups, suggesting that the biphasic ventilatory response is specific to hypoxia. Additional experiments assessed hypoxic hypometabolism, and decreased metabolic rate does not appear to explain the biphasic HVR in the youngest quail chicks. We conclude that newborn quail exhibit a biphasic HVR similar to that observed in newborn mammals.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.