title: Effects of daily environmental enrichment on behavior and dendritic spine density in hippocampus following neonatal hypoxia-ischemia in the rat.
abstract: Hypoxia-ischemia (HI) is the main cause of mortality in the perinatal period and morbidity, in survivors, which is characterized by neurological disabilities. The immature brain is highly susceptible to hypoxic-ischemic insult and is responsive to environmental stimuli, such as environmental enrichment (EE). Previous results indicate that EE recovered memory deficits in adult rats without reversing hippocampal atrophy related to HI. The aim of this study was to investigate behavioral performance in the open field and rota-rod apparatuses, in object recognition and inhibitory avoidance tasks, as well as dendritic spine density in the hippocampus, in rats undergoing HI and exposed to EE. Seven-day old male rats were submitted to the HI procedure and divided into 4 groups: control maintained in standard environment (CTSE), controls submitted to EE (CTEE), HI in standard environment (HISE) and HI in EE (HIEE). Behavioral and morphological parameters were evaluated 9 weeks after the environmental stimulation. Results indicate impairment in the object recognition task after HI that was recovered by enrichment; however the aversive memory impairment in the inhibitory avoidance task shown by hypoxic-ischemic rats was independent of the environment condition. Hypoxic-ischemic groups showed more crossing responses during the first minute in the open field, when compared to controls, but no differences were found between experimental groups in the rota-rod test. Dendritic spine density in the CA1 subfield of the right hippocampus (ipsilateral to the artery occlusion) was decreased after the HI insult, and increased in enriched controls; interestingly enriched HI rats did not differ from CTSE. In conclusion, EE was effective in recovering declarative memory impairment in object recognition and preserved hippocampal dendritic spine density loss after neonatal HI injury.
authors.affiliation: Programa de Pós-graduação em Neurociências, ICBS, Universidade Federal do Rio Grande do Sul, Brazil.
authors.forename: Joseane Jiménez
authors.initials: JJ
authors.lastname: Rojas
authors.forename: Bruna Ferrary
authors.initials: BF
authors.lastname: Deniz
authors.forename: Patrícia Maidana
authors.initials: PM
authors.lastname: Miguel
authors.forename: Ramiro
authors.initials: R
authors.lastname: Diaz
authors.forename: Erica do Espírito-Santo
authors.initials: Edo E
authors.lastname: Hermel
authors.forename: Matilde
authors.initials: M
authors.lastname: Achaval
authors.forename: Carlos Alexandre
authors.initials: CA
authors.lastname: Netto
authors.forename: Lenir Orlandi
authors.initials: LO
authors.lastname: Pereira
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001362:Avoidance Learning / Q000502:physiology; D001522:Behavior, Animal / Q000502:physiology*; D049229:Dendritic Spines / Q000473:pathology*; D004195:Disease Models, Animal; D004777:Environment; D005106:Exploratory Behavior / Q000502:physiology; D006624:Hippocampus / Q000473:pathology* / Q000648:ultrastructure; D020925:Hypoxia-Ischemia, Brain / Q000451:nursing / Q000473:pathology / Q000503:physiopathology; D007266:Inhibition, Psychological; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D021641:Recognition, Psychology / Q000502:physiology; D045442:Rotarod Performance Test; D016622:Silver Staining