Effect of skilled reaching training and enriched environment on generation of oligodendrocytes in the adult sensorimotor cortex and corpus callosum

Silke Keiner, Fanny Niv, Susanne Neumann, Tanja Steinbach, Christian Schmeer, Katrin Hornung, Yvonne Schlenker, Martin Förster, Otto W. Witte, Christoph Redecker

Increased motor activity or social interactions through enriched environment are strong stimulators of grey and white matter plasticity in the adult rodent brain. In the present study we evaluated whether specific reaching training of the dominant forelimb (RT) and stimulation of unspecific motor activity through enriched environment (EE) influence the generation of distinct oligodendrocyte subpopulations in the sensorimotor cortex and corpus callosum of the adult rat brain. Animals were placed in three different housing conditions: one group was transferred to an EE, a second group received daily RT, whereas a third group remained in the standard cage. Bromodeoxyuridine (BrdU) was applied at days 2-6 after start of experiments and animals were allowed to survive for 10 and 42 days. Enriched environment and daily reaching training of the dominant forelimb significantly increased the number of newly differentiated GSTπ(+) oligodendrocytes at day 10 and newly differentiated CNPase(+) oligodendrocytes in the sensorimotor cortex at day 42. The myelin level as measured by CNPase expression was increased in the frontal cortex at day 42. Distribution of newly differentiated NG2(+) subpopulations changed between 10 and 42 days with an increase of GSTπ(+) subtypes and a decrease of NG2(+) cells in the sensorimotor cortex and corpus callosum. Analysis of neuronal marker doublecortin (DCX) showed that more than half of NG2(+) cells express DCX in the cortex. The number of new DCX(+)NG2(+) cells was reduced by EE at day 10. Our results indicate for the first time that specific and unspecific motor training conditions differentially alter the process of differentiation from oligodendrocyte subpopulations, in particular NG2(+)DCX(+) cells, in the sensorimotor cortex and corpus callosum.