Characterization of pontine neurons which respond to hypoxia in fetal sheep

Neurosci Lett. 1999 Apr 30;266(1):33-6. doi: 10.1016/s0304-3940(99)00249-9.

Abstract

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.

MeSH terms

  • Animals
  • Catecholamines / physiology
  • Female
  • Fetus / physiology
  • Hypoxia / physiopathology*
  • Immunohistochemistry
  • Neurons / physiology*
  • Parasympathetic Nervous System / physiology
  • Phenotype
  • Pons / cytology
  • Pons / physiopathology*
  • Pregnancy
  • Proto-Oncogene Proteins c-fos / metabolism
  • Sheep
  • Spinal Cord / cytology
  • Spinal Cord / metabolism
  • Tyrosine 3-Monooxygenase / metabolism
  • gamma-Aminobutyric Acid / physiology

Substances

  • Catecholamines
  • Proto-Oncogene Proteins c-fos
  • gamma-Aminobutyric Acid
  • Tyrosine 3-Monooxygenase