BDNF and Huntington disease: As exercise increases BDNF production [20] and BDNF can reduce the severity of HD symptoms [40], it is possible that in running R6/2 mice BDNF helps to maintain cellular integrity. BDNF determination in running and non-running mice did not reveal significant increases in protein content in soluble extracts from the striatum of R6/2 mice, consistent with a previous report [41].