Learned defense response to hypoxia in newborn mice.
In newborns, hypoxia elicits defensive behaviors including awakening from sleep, body movements and crying. An inability to produce this defense response is a risk factor for sudden infant death syndrome and other respiratory control disorders. In this study, we examined the possibility that the defense response to hypoxia in newborns is partly determined by early exposure to hypoxia. We explored this possibility in 6-day-old mice, which resemble human preterm infants of approximately 25-30 weeks' gestational age. Ultrasonic vocalizations (USVs) were recorded as a marker for the defense response to hypoxia. In a conditioning experiment, newborn mice were exposed to two artificial odors (conditioned stimuli, CS). For acquisition (two trials), pups were exposed to one odor (CS+) in a hypoxic gas mixture (10% O2, which was the unconditioned stimulus, US) and to another odor (CS-) in air. Then, the pups were exposed to each odor while breathing air. Newborn mice produced significantly more USVs when exposed to the odor previously paired with hypoxia than to the control odor. Thus, associative learning may shape the defense response to hypoxia in newborns.
Bollen
Bieke
B
INSERM, U676, Robert-Debré Teaching Hospital, 75019 Paris, France, and Laboratory of Biological Psychology, Department of Psychology, University of Leuven, B-3000 Leuven, Belgium.
Bouslama
Myriam
M
Matrot
Boris
B
D'Hooge
Rudi
R
Van den Bergh
Omer
O
Gallego
Jorge
J
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001245:Association Learning / Q000502:physiology; D001273:Atmosphere Exposure Chambers; D001522:Behavior, Animal / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology; D003463:Cues; D005260:Female; D000860:Hypoxia / Q000523:psychology*; D051379:Mice; D009812:Odorants; D011247:Pregnancy; D012903:Smell / Q000502:physiology; D014828:Vocalization, Animal / Q000502:physiology