Fig. 1.

The GLP-1 receptor is both expressed and functional on cultured mouse primary cortical neurons, and its activation provides neuroprotection. a One step RT–PCR demonstrating GLP-1R mRNA expression in neuronal cell cultures. The predicted RT–PCR product size is 190 bp. The standard, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), was evident across all lanes (not shown). Lane 1 positive control; 2 negative control, respectively, which for the former RNA was extracted from Chinese hamster ovary cells stably transfected with rodent GLP-1R; 3 RNA extracted from primary neuron cultures. b Ex-4 (100 nM) stimulated cAMP release from primary cortical neurons that was markedly elevated (40-fold) versus resting (unstimulated) cells (N = 3, *p < 0.001; Student’s t test). c, d Pretreatment with Ex-4 protected primary cortical neuron cultures from glutamate (10 μM) and SH-SY5Y cells from glutamate (100 mM) and oxidative stress (H₂O₂ 100 and 200 μM)-induced cellular toxicity, as assessed in (c) by MTS assay at 48 h [N ≥ 3 per treatment group, *p < 0.05 Dunnett’s t test vs. cellular insult; N.S. not significantly different from control (no treatment group)], in (d) by MTS assay at 24 h (N ≥ 3 per treatment group, *p < 0.05, ***p < 0.001, Dunnett’s t test with Bonferonni correction), and in (e) by LDH assay at 24 h (N ≥ 3 per treatment group, *p < 0.05, **p < 0.01, and ***p < 0.001, Dunnett’s t test with Bonferonni correction)