Sz. Yuan et al., ADRENALECTOMY REDUCES THE ABILITY OF NEWBORN RATS TO GASP AND SURVIVEANOXIA, Acta Physiologica Scandinavica, 159(4), 1997, pp. 285-292
The ventilatory response to anoxia in unanaesthetized rat pups of 1 an
d 8 days of age was studied. Ventilation was recorded by barometric pl
ethysmography. During acute anoxia (100% N-2) animals of both ages res
ponded with hyperpnoea, primary apnoea, hypoxic gasping and secondary
apnoea. After secondary gasping, occasional gasps occurred. If oxygen
was administered during the gasping period, all animals survived throu
gh autoresuscitation. The duration of the period of hypoxic gasping wa
s significantly longer in the 1-day-old animals. Adrenalectomy reduced
the length of this period in both 1- and 8-day-old animals. In a seco
nd series of experiments, the effect of adrenergic antagonists on auto
resuscitation was examined. Pretreatment with the non-selective alpha-
receptor antagonist phentolamine reduced the duration of gasping in 1-
day-old rats, but prolonged this duration in 8-day-old rats. The non-s
elective beta-receptor antagonist propranolol did not affect the durat
ion of gasping in 1-day-old rats, whereas it prolonged this period in
the older animals. We conclude that proper duration of gasping during
anoxia is dependent on intact adrenal function and that the adrenal gl
ands therefore play an important role in autoresuscitation from anoxia
during postnatal life. The underlying mechanism appears to involve al
pha-adrenergic receptors.