Short-term environmental enrichment increases adult neurogenesis in the dentate gyrus of type 1 diabetic mice.

BEAUQUIS J; ROIG P; DE NICOLA AF; SARAVIA F

Buzios, Brasil

Congreso; Primer Congreso IBRO/LARC de Neurociencias para Latinoamérica, Caribe y Península Ibérica.; 2008

International Brain Research Organization

Objectives Diabetes affects several body systems including the CNS. The hippocampus is involved in cognitive processing, and neurogenesis in the hippocampal dentate gyrus (DG) is essential for some types of learning and memory. We previously found diminished neurogenesis in diabetic mice which is reversed by antidepressant treatment (Eur J Neurosci, 23:1539, 2006). In aging or depression, the exposure to a rich environment is able to increase neurogenesis in the DG. Our aim was to test if a short environmental enrichment (EE) was capable of reversing the low neurogenesis in the DG of type 1 diabetic mice. Methods Adult male C57BL/6 mice were rendered diabetic by streptozotocin. Diabetic and control mice were exposed for 10 days to either standard caging (SC) or EE. The EE involved more mice per cage, larger cages with toys, tubes, houses and nesting material. No running wheel was present to avoid the influence of physical exercise on neurogenesis. Bromodeoxyuridine (BrdU) was injected 24 h before starting the EE. We performed immunohistochemistry to study cell survival (BrdU), neuronal differentiation (BrdU-Tuj1 double immunofluorescence) and dendritic length of new neurons (DCX). Results Cell survival was reduced in diabetic animals in SC, and exposure to EE significantly increased it (CTL-SC 1076±71.44; CTL-EE 1254±130.0; DIAB-SC 579.2±100.5, P<0.05 vs CTL-SC; DIAB-EE 1194±186.9, P<0.05 vs DIAB-SC; mean±SEM number of BrdU+ cells/DG). Neuronal differentiation was lower in diabetic animals with SC and exposure to EE augmented it (CTL-SC 0,89±0,01; CTL-EE 0,93±0,009; DIAB-SC 0,79±0,02, P<0.05 vs CTL-SC; DIAB-EE 0,89±0,02, P<0.01 vs DIAB-SC; mean±SEM ratio of BrdU+Tuj1+/BrdU+ cells). We found decreased dendritic length in DCX+ cells of diabetic animals and EE increased length to control levels. Conclusions Our results showed that a short-term exposure to a rich environment increased adult hippocampal neurogenesis and positively modulated the dendritic length of newborn neurons in diabetic mice. Further investigation is needed to identify potential mediators of these events and to correlate neurochemical results with cognitive impairments associated with the disease.