GRM5 and Parkinson disease: In order to investigate whether the increased mGluR5 level in the DLB and PD cases and in the alpha-syn tg mice was associated with a concomitant increase in the levels of downstream signaling components, levels of total and phosphorylated ERK, Elk–1 and CREB were examined in the cytoplasmic and membrane fractions from the frontal cortex.