Severe alcohol-induced neuronal deficits in the hippocampus and neocortex of neonatal mice genetically deficient for neuronal nitric oxide synthase (nNOS).
Alcohol can severely damage the developing brain, and neuronal loss is a critical component of this injury. Thus, identification of molecular factors that ameliorate alcohol-induced neuronal loss is of great importance. Previous in vitro work has demonstrated that nitric oxide (NO) protects neurons against alcohol toxicity. We tested the hypothesis that neonatal mice carrying a null mutation for neuronal nitric oxide synthase (nNOS), the enzyme that synthesizes NO in neurons, have an increased vulnerability to alcohol-induced neuronal loss in the neocortex and hippocampus. Wildtype mice and nNOS-/- mice received ethanol (0.0, 2.2, 3.3, or 4.4 g/kg) daily over postnatal days (P) 4-9 and were sacrificed on P10. The number of hippocampal CA1 and CA3 pyramidal cells, dentate gyrus granule cells, and neocortical neurons were determined using stereological methods. Alcohol pharmacokinetics did not differ between wildtype and nNOS-/- strains. Alcohol induced dose-dependent reductions in all four neuronal populations, and the losses were substantially more severe in the nNOS-/- mice than in wildtype. Furthermore, the threshold dose of alcohol to induce cell death was lower in the nNOS-/- mice than in the wildtype mice for all neuronal populations. While nNOS deficiency worsened alcohol-induced neuronal losses, the magnitude of this exacerbation varied among brain regions and depended on alcohol dose. These results demonstrate that nNOS deficiency decreases the ability of developing neurons in vivo to survive the toxic effects of alcohol and strengthen the hypothesis that NO exerts a neuroprotective effect against alcohol toxicity in the developing brain.
Bonthius
Daniel J
DJ
Neuroscience Program, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA. daniel-bonthius@uiowa.edu
McKim
Ross A
RA
Koele
Lindsey
L
Harb
Harb
H
Kehrberg
Ana Hutton
AH
Mahoney
Jo
J
Karacay
Bahri
B
Pantazis
Nicholas J
NJ
D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002452:Cell Count / Q000379:methods; D002492:Central Nervous System Depressants / Q000097:blood / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000097:blood / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019579:Neocortex / Q000187:drug effects / Q000473:pathology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D052248:Nitric Oxide Synthase Type I / Q000172:deficiency*
D002492:Central Nervous System Depressants; D000431:Ethanol; D052248:Nitric Oxide Synthase Type I