E. Canet et al., POSTNATAL MATURATION OF PERIPHERAL CHEMORECEPTOR VENTILATORY RESPONSETO O-2 AND CO2 IN NEWBORN LAMBS, Journal of applied physiology, 80(6), 1996, pp. 1928-1933
Although studies on lambs have shown that carotid body sensitivity to
O-2 is reset postnatally, it is still unknown whether O-2 and CO2 peri
pheral chemoreflexes undergo parallel postnatal maturation. The presen
t study was designed to analyze maturation of O-2 and CO2 peripheral c
hemoreflexes in 10 lambs at <24 h and at 12 days of age. We measured t
he ventilatory (V over dot E) response to three tidal breaths of pure
N-2 or 13% CO2 in air. Overall, the N-2 peripheral chemoreflex increas
ed significantly with maturation [V over dot E/end-tidal O-2 (ml . min
(-1) . kg(-1) . Torr(-1)) = 2.94 +/- 0.91 at <24 h vs. 5.13 +/- 0.59 a
t 12 days, P < 0.05], whereas the CO2 peripheral chemoreflex did not c
hange (V over dot E/end-tidal CO2 = 7.04 +/- 0.98 at <24 h vs. 7.75 +/
- 1.07 at 12 days, not significant), We conclude that the CO2 peripher
al chemoreflex does not change in awake lambs within the time frame st
udied, in contrast to a marked postnatal maturation of the O-2 periphe
ral chemoreflex. The different time courses of O-2 and CO2 peripheral
chemoreflex maturation support the concept that carotid body sensitivi
ties to O-2 and CO2 do not depend on the same basic mechanisms.