Rescue of BDNF expression by the thalamic parafascicular nucleus with chronic treatment with the mGluR2/3 agonist LY379268 may contribute to the LY379268 rescue of enkephalinergic striatal projection neurons in R6/2 Huntington's disease mice

We have found that daily subcutaneous injection with a maximum tolerated dose of the mGluR2/3 agonist LY379268 (20 mg/kg) beginning at 4 weeks of age dramatically improves the motor, neuronal and neurochemical phenotype in R6/2 mice, a rapidly progressing transgenic model of Huntington's disease (HD). We also previously showed that the benefit of daily LY379268 in R6/2 mice was associated with increases in corticostriatal brain-derived neurotrophic factor (BDNF), and in particular was associated with a reduction in enkephalinergic striatal projection neuron loss. In the present study, we show that daily LY379268 also rescues expression of BDNF by neurons of the thalamic parafascicular nucleus in R6/2 mice, which projects prominently to the striatum, and this increase too is linked to the rescue of enkephalinergic striatal neurons. Thus, LY379268 may protect enkephalinergic striatal projection neurons from loss by boosting BDNF production and delivery via both the corticostriatal and thalamostriatal projection systems. These results suggest that chronic treatment with mGluR2/3 agonists may represent an approach for slowing enkephalinergic neuron loss in HD, and perhaps progression in general.