Effects of undernourishment, recurrent seizures and enriched environment during early life in hippocampal morphology

Abstract

It has been recently shown that enriched environment led to a significant benefit in learning and retention of visual-spatial memory, being able to reverse the cognitive impairment generated by undernourishment and recurrent seizures. We investigated the hippocampal morphological effects of recurrent seizures and undernourishment early in life in Wistar rats and the possible benefits produced by the enriched environment in these conditions. The morphological parameters stereologically evaluated were hippocampal volume, thickness of pyramidal stratum of the CA1 subfield and neuronal and glial densities in the same subfield. Male Wistar rats were divided into eight groups including nourished, nourished+enriched environment, nourished+recurrent seizures, nourished+recurrent seizures+enriched environment, undernourished, undernourished+enriched environment, undernourished+recurrent seizures and undernourished+recurrent seizures+enriched environment. Undernourishment model consisted in nutritional deprivation regimen from post-natal day 2 (P2) to P15. From P8 to P10, recurrent seizures group were induced by flurothyl three times per day. Enriched environment groups were exposed between P21 and P51. Our main findings were: (1) animals submitted to the enriched environment showed an increased hippocampal volume; (2) enriched environment promotes increases in the thickness of the pyramidal layer in hippocampal CA1 subfield in animals nourished and undernourished with recurrent seizures; (3) undernourishment during early development decreased neuronal density in CA1 and CA3 subfields. Our findings show that these three conditions induces important changes in hippocampal morphology, the most deleterious changes are induced by undernourishment and recurrent seizures, while more beneficial morphological changes are produced by enriched environment.

Increased protein expression levels of pCREB, BDNF and SDF-1/CXCR4 in the hippocampus may be associated with enhanced neurogenesis induced by environmental enrichment

“…Although the underlying mechanisms remain to be elucidated, it is possible that cognitive improvements associated with EE in the normal brain are associated with the enhanced neural plasticity occurring at various levels in the brain. The evidence for enhanced neural plasticity includes neurogenesis, multiple structural changes, increases in neurotrophic factors, and essential proteins and genes involved in neuronal plasticity, as well as alterations in neurotransmitters and receptors (11,12,32).…”

Enriched Environment Altered Aberrant Hippocampal Neurogenesis and Improved Long-Term Consequences After Temporal Lobe Epilepsy in Adult Rats

“…Possibly, neural plasticity at several levels in the brain induced by EE, including multiple structural changes, neurogenesis, synaptogenesis, increase of neurotrophic factors, and essential genes and proteins involved in the neuronal plasticity and alterations in neurotransmitters or receptors were involved in the cognitive improvements associated with EE in the normal brain (Alvarez et al 2014;Leger et al 2014;Monteiro et al 2014). In immature rats, EE has been shown to reverse the cognitive decline during epileptogenesis (Faverjon et al 2002;Rutten et al 2002).…”

Association of Socioeconomic Status and Brain Injury With Neurodevelopmental Outcomes of Very Preterm Children

“…However, the neuroscience literature suggests many examples through which enriched environments can mitigate the impact of early-life brain injuries. 8 , 9 , 10 , 11 , 12 …”