Characterization of pontine neurons which respond to hypoxia in fetal sheep.
Hypoxia causes apnea and postural muscle hypotonia in fetal sheep, a response thought to arise by descending inhibition from a group of lateral pontine neurons that express FOS protein after hypoxia. To determine the neurochemical phenotype, and whether these neurons project to the cervical spinal cord, the retrograde tracer CTB-gold was injected into the C5-C8 ventral horn of four fetal sheep at 110 days gestation. Then, at 135 days each fetus was made hypoxic for 2 h by allowing the mother to breathe 7-8% O2. Immunocytochemistry showed that FOS-positive neurons in the subcoeruleus and Kolliker-Fuse regions of the pons were catecholaminergic, but not cholinergic or GABAergic, and a proportion of them contained CTB-gold particles, indicating direct connection with the cervical spinal cord. We suggest that these pontine neurons inhibit respiratory and postural muscle activities during hypoxia in fetal sheep.
Nitsos
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Department of Physiology, Monash University, Clayton, Victoria, Australia.
Walker
D W
DW
D000818:Animals; D002395:Catecholamines / Q000502:physiology; D005260:Female; D005333:Fetus / Q000502:physiology; D000860:Hypoxia / Q000503:physiopathology*; D007150:Immunohistochemistry; D009474:Neurons / Q000502:physiology*; D010275:Parasympathetic Nervous System / Q000502:physiology; D010641:Phenotype; D011149:Pons / Q000166:cytology / Q000503:physiopathology*; D011247:Pregnancy; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D012756:Sheep; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D002395:Catecholamines; D016760:Proto-Oncogene Proteins c-fos; D005680:gamma-Aminobutyric Acid; D014446:Tyrosine 3-Monooxygenase