Neurodegeneration, neuronal loss, and neurotransmitter changes in the adult guinea pig with perinatal asphyxia

Abstract

There is only limited morphologic information on long-term alterations and neurotransmitter changes after perinatal asphyxia, and no long-term study showing neurodegeneration has been reported so far. We used an animal model for perinatal asphyxia well documented in the rat to investigate the guinea pig as a species highly mature at birth. Cesarean section was performed on full-term pregnant guinea pigs, and pups, still in membranes, were placed into a water bath at 37°C for asphyxia periods from 2 to 4 min. Thereafter pups were given to surrogate mothers and examined at 3 mo of age. We studied brain areas reported to be hypoxia-sensitive. Neurodegeneration was evaluated by fluoro-jade, neuronal loss by Nissl, reactive gliosis by glial fibrillary acidic protein staining, and differentiation by neuroendocrine-specific protein C immunoreactivity. We tested tyrosine hydroxylase, the vesicular monoamine transporter, and dopamine β-hydroxylase, representing the monoaminergic system; the vesicular acetylcholine transporter; and the excitatory amino acid carrier 1. Neurodegeneration was evident in cerebellum, hippocampal area CA1, and hypothalamus, and neuronal loss could be observed in cerebellum and hypothalamus; gliosis was observed in cerebellum, hippocampus, hypothalamus, and parietal cortex; dedifferentiation was found in hypothalamus and striatum; and monoaminergic, cholinergic, and amino acidergic deficits were shown in several brain regions. The major finding of the present study was that neurodegeneration and dedifferentiation evolved in the guinea pig, a species highly mature at birth. The relevance of this contribution is that a simple animal model of perinatal asphyxia resembling the clinical situation of intrauterine hypoxia-ischemia and presenting with neurodegeneration was characterized.