Photomicrograph comparing Y10B labeling between untreated (A) and mGluR agonist-treated (B) sides of the same brain slice.

<p>In this example, the group I selective mGluR agonist, DHPG, was applied to NM on one side of the slice for 1 hr. Tissue sections were immunolabeled with Y10B, a monoclonal antibody that recognizes a ribosomal epitope. There is darker Y10B immunolabeling of NM neurons on the drug-treated side of the brain section. (C) Percent differences in gray scale density for Y10B labeling between NM neurons on untreated versus drug-treated sides of the same brain slice ((mean treated density-mean untreated density)/mean treated density*100). Bars indicate standard error of the mean. Positive numbers indicate that the treated side had greater labeling for Y10B. Different groups of slices (n = 4 per group) received unilateral application of vehicle, L-glutamic acid, a general mGluR agonist, ACPD, an mGlu group I agonist, DHPG, or an mGlu-group II-selective agonist, LY354740. The vehicle-treated control slices showed no difference in Y10B labeling between sides while treatment with each agonist resulted in a darker Y10B labeling on the drug-treated side of the slice. (D) Dose-response curve plotting the mean percent difference in gray scale density for Y10B labeling following unilateral application of varying concentrations of L-glutamic acid. Positive numbers indicate that the treated side had darker Y10B immunolabeling. As concentration in the ejection pipette increased, the treated NM neurons first showed darker Y10B immunolabeling (at 1 mM) and then showed lighter immunolabeling (at 10 mM). The percent difference in labeling between opposite sides of the same slices was statistically lower at 10 mM than at any other concentration and the percent difference at 1 mM was statistically greater than at 0.01 mM but only marginally greater (p = 0.06) than the 0.1 mM group. These data suggest that the effect of glutamate transitions from neuroprotection at moderate concentrations, to neurotoxicity at high concentrations.