Environmental enrichment facilitates long-term potentiation in embryonic striatal grafts.

Abstract

BACKGROUND: Housing animals in an enriched environment improves motor and cognitive performance and anatomical connectivity in rodent lesion models of Huntington disease and transplantation of embryonic striatal grafts. OBJECTIVE: The authors evaluate the extent to which environmental enrichment can modify synaptic plasticity in the host-graft neuronal circuitry to try to find a physiological substrate for the observed improvements. METHODS: C57BL/6 mice, housed in enriched or standard environments, received unilateral quinolinic acid lesions of the striatum, followed by embryonic striatal grafts. Then, 3 months posttransplantation, synaptic physiology and plasticity were evaluated by extracellular recording from in vitro striatal slices. RESULTS: Environmental enrichment had no effect on the chance of long-term depression (LTD) induction or expression of LTD from either normal or grafted striatum. In contrast, enrichment increased the chance of long-term potentiation (LTP) induction and level of expression associated with increased levels of brain-derived neurotrophic factor within both the intact and grafted striatum compared with levels in the striatum of animals housed in standard environments. CONCLUSIONS: Environmental enrichment induces changes in host-graft corticostriatal LTP, thus providing a potential physiological substrate for the enrichment-induced improvement in motor and cognitive performance. The effect may be mediated by modulation of the trophic environment in which the grafted cells develop and integrate.