Changes in open field behavior, spatial memory, and hippocampal parvalbumin immunoreactivity following enrichment in rats exposed to neonatal anoxia.

Behavioral and neurochemical changes following enriched housing were studied in Wistar rats neonatally exposed to anoxia (100% N2 for 25 min at approximately 30 h after birth) or to sham treatment. Neonatal anoxia provoked transient hyperactivity during the P25-P40 period, and spatial memory disturbances persisting into adult life. Enriched housing, from P21, at weaning, to P60, improved behavior in open field and spatial memory abilities in a water maze, reducing the deficits that followed neonatal anoxia. Changes in the expression of the calcium binding protein parvalbumin were present in the CA1, CA3, and DG regions of the hippocampus in both sham-treated and anoxic rats exposed to enrichment. The present findings give further support to the evidence of a positive effect of enriched housing on behavior and learning of normal and lesioned animals, which is sustained by modifications in the neuronal activity, and suggest that modifications in the environment can be useful to counteract the development of some neurological disturbances that follow neonatal insults, e.g., perinatal asphyxia.