Time Course of the Response of Carotid Chemoreceptors to Sudden Rise of Inspired co2 in the Newborn Kitten

The carotid body chemoreceptors are the main sensors for the level of arterial PO2 involved in the ventilatory control. It is well recognized that they also contribute to the ventilatory response to changes in PaCO2. Electrophysiological recordings of carotid chemoreceptor activity in adult animals show that they present a rapid response to sudden step rise of PCO2 in the arterial blood (Dutton et al., 1967; Fitzgerald et al., 1969; Black et al.,1971). It is still appreciable during hyperoxia and is enhanced by hypoxia (Fitzgerald and Parks, 1971;Lahiri et al., 1975, 1982). On the other hand, it has been established that an adaptation of the ventilatory response to CO2 occurs within seconds of a peak response (Dutton et al., 1967). Similarly, the carotid chemoreceptors appear to adapt (Black et al.,1971), at least in hypoxia or under specific stimulation (Lahiri et al. 1982, 1989). However, these results have only been observed in adult animals. In newborns, the weak chemosensory reactivity of carotid body is well documented (Blanco et al., 1984) but no information on the neonatal development either of the dynamic CO2- response of peripheral chemoreceptors or of the O2-CO2 interaction was available.