Postnatal age influences the ability of rats to autoresuscitate from hypoxic-induced apnea

Failure to autoresuscitate from apnea by gasping has been suggested to have a role in sudden infant death. Little is known, however, about the factors that influence the ability of gasping to sustain life during acute hypoxia in the newborn. The present experiments were carried out on 105 rat pups t o investigate the influence of postnatal age on the time to last gasp durin g a single hypoxic exposure and on the ability to autoresuscitate from prim ary apnea during repeated hypoxic exposures. On days 1-2, 5-6, 10-11, 15-16 , and 19-20 postpartum, each pup was placed into a temperature-controlled c hamber regulated to 37 +/- 1 degrees C and was exposed either to a single p eriod of hypoxia produced by breathing an anoxic gas mixture (97% N-2-3% CO 2), and the time to last gasp was determined, or repeated exposure to hypox ia was performed, and the ability to autoresuscitate from primary apnea was determined. Increases in postnatal age decreased the time to last gasp fol lowing a single hypoxic exposure and decreased the number of successful aut oresuscitations following repeated hypoxic exposures. Thus our data provide evidence that postnatal age influences protective responses that may preve nt death during hypoxia as may occur during episodes of prolonged sleep apn ea.