BDNF and ring chromosome 6: This is consistent with other studies that showed a relatively low baseline level of BDNF in astrocytes [41] but an upregulation of astrocytic BDNF expression under pathological conditions induced by MK-801, an N-methyl-D-aspartic acid (NMDA) receptor antagonist, in vitro [42], and treatment of glatiramer acetate in the R6/2 HD mouse model in vivo [41].