Correlations between brainstem NMDA receptor changes and active neuronal cell death after intermittent hypercapnic hypoxia in the developing piglet

• Published in: Brain research Vol. 975; no. 1; pp. 141 - 148
• Main Authors: Machaalani, R., Waters, K.A.
• Format: Journal Article
• Language: English
• Published: London Elsevier B.V 13-06-2003; Amsterdam Elsevier; New York, NY
• Subjects: Ageing, cell death; Animals; Animals, Newborn - physiology; Apoptosis; Biological and medical sciences; Brain Stem - metabolism; Brain Stem - pathology; Cell Death - physiology; Cell physiology; Co-localization; Fundamental and applied biological sciences. Psychology; Hypercapnia - pathology; Hypoxia, Brain - pathology; Immunohistochemistry; In Situ Nick-End Labeling; Medulla; Medulla Oblongata - pathology; Molecular and cellular biology; Neurons - pathology; Non-NR1; NR1; Receptors, N-Methyl-D-Aspartate - metabolism; SIDS; Swine; TUNEL; Vagus Nerve - pathology; Disorders of the nervous system; Co-localization; TUNEL; SIDS; Medulla; NR1; Non-NR1; Apoptosis; Oxygen; Brain stem; Central nervous system; Environmental factor; Glutamate receptor; Pig; Hypercapnia; Vertebrata; Mammalia; Cell death; Development; Hypoxia; Artiodactyla; NMDA receptor; Ungulata; Brain (vertebrata)
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(03)02603-9

The role of the
N-methyl-
d-aspartate (NMDA) receptor in cell death was evaluated in the piglet brainstem after exposure to intermittent hypercapnic hypoxia (IHH). Study groups comprised controls (
n=6) and piglets exposed to IHH on 2 (
n=6) or 4 (
n=5) successive days prior to euthanasia. All piglets had the caudal medulla evaluated at 13–14 days of age using double immunohistochemistry for TUNEL and the NMDA receptor 1 (NR1) subunit. The percent of TUNEL positive neurons amongst NR1 (% TUN in NR1) and non-NR1 neurons (% TUN in non-NR1) was determined in eight nuclei. After 2 days of IHH, %TUN in NR1 was increased in the dorsal motor nucleus of the vagus (DMNV,
P=0.007) and the inferior olivary nucleus (ION,
P=0.05). After 2 days IHH, %TUN in non-NR1 neurons was increased in the lateral reticular nucleus (LRt,
P=0.05), nucleus of the solitary tract (NTS,
P=0.004) and gracile nucleus (
P=0.05). After 4days IHH, the increase of %TUN in NR1 was sustained in the ION (
P=0.05), while %TUN in non-NR1 neurons was sustained in NTS (
P=0.04) and LRt (
P=0.006). Daily IHH exposure induces neuronal death within NR1 and non-NR1 neurons, but the neuronal phenotype is consistent within affected brainstem nuclei. Involvement of the NMDA receptor tended to occur in nuclei with higher basal NR1 expression, and thus occurred in nuclei relevant to cardiorespiratory function. We speculate that IHH exposures, such as occurs during obstructive apnea or facial entrapment in prone sleeping during infancy, can induce abnormalities of cardiorespiratory control.