title: Effects of environmental enrichment on blood vessels in the optic tract of malnourished rats: A morphological and morphometric analysis.
abstract: OBJECTIVE
  This study aimed to compare the effects of environmental enrichment in nourished (on a diet containing 16% protein) and malnourished (on a diet containing 6% protein) rats during the critical period of brain development, specifically focusing on the optic nerve.
  
  
  METHODS
  By means of morphologic and morphometric assessment of the optic nerve, we analyzed the changes caused by diet and stimulation (environmental enrichment) on postnatal day 35, a time point ideal for such morphological analysis since developmental processes are considered complete at this age.
  
  
  RESULTS
  Malnourished animals presented low body and brain weights and high body-to-brain weight ratio compared to well-nourished rats. Furthermore, malnourished animals showed morphological changes in the optic nerve such as edema and vacuolization characterized by increased interstitial space. The malnourished-stimulated group presented lesions characteristic of early protein malnutrition but were milder than lesions exhibited by malnourished-non-stimulated group. The morphometric analysis revealed no difference in glial cell density between groups, but there was significantly higher blood vessel density in the stimulated rats, independent of their nutritional condition.
  
  
  CONCLUSIONS
  Our data indicate that protein malnutrition imposed during the critical period of brain development alters the cytoarchitecture of the optic nerve. In addition, we affirm that a 1-hour exposure to an enriched environment everyday was sufficient for tissue preservation in rats maintained on a low-protein diet. This protective effect might be related to angiogenesis, as confirmed by the increased vascular density observed in morphometric analyses.
authors.affiliation: a Faculty of Philosophy Sciences and Letters of Ribeirão Preto, Department of Psychology , University of São Paulo , Brazil.
authors.forename: Everton Horiquini
authors.initials: EH
authors.lastname: Barbosa
authors.affiliation: b Faculty of Medicine of Ribeirão Preto, Department of Surgery and Anatomy , University of São Paulo , Brazil.
authors.forename: Roberto Oliveira
authors.initials: RO
authors.lastname: Soares
authors.affiliation: a Faculty of Philosophy Sciences and Letters of Ribeirão Preto, Department of Psychology , University of São Paulo , Brazil.
authors.forename: Natália Nassif
authors.initials: NN
authors.lastname: Braga
authors.affiliation: a Faculty of Philosophy Sciences and Letters of Ribeirão Preto, Department of Psychology , University of São Paulo , Brazil.
authors.forename: Sebastião de Sousa
authors.initials: Sde S
authors.lastname: Almeida
authors.affiliation: b Faculty of Medicine of Ribeirão Preto, Department of Surgery and Anatomy , University of São Paulo , Brazil.
authors.forename: João-José
authors.initials: JJ
authors.lastname: Lachat
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001808:Blood Vessels / Q000473:pathology / Q000503:physiopathology; D004195:Disease Models, Animal; D004487:Edema / Q000209:etiology; D005260:Female; D007774:Lactation; D008297:Male; D039382:Maternal Nutritional Physiological Phenomena; D018919:Neovascularization, Physiologic; D009410:Nerve Degeneration / Q000209:etiology / Q000517:prevention & control*; D009900:Optic Nerve / Q000098:blood supply / Q000473:pathology / Q000503:physiopathology; D065866:Optic Tract / Q000098:blood supply* / Q000473:pathology / Q000503:physiopathology; D009929:Organ Size; D010775:Photic Stimulation; D011488:Protein Deficiency / Q000473:pathology / Q000503:physiopathology*; D011897:Random Allocation; D017208:Rats, Wistar; D014617:Vacuoles / Q000473:pathology; D015430:Weight Gain
keywords: Angiogenesis; Blood vessels; Cytoarchitecture; Environmental enrichment; Glial cells; Malnutrition; Optic nerve; Protein deficiency