Figure 3.

Pharmacology of dopamine/glutamate-induced apoptosis of YAC128 MSNs. A, Inhibition of D₁-class DARs protects YAC128 MSNs from dopamine (Dop)/glutamate-induced apoptosis. The fraction of TUNEL-positive nuclei is shown for WT and YAC128 (YAC) MSNs incubated for 8 h in the presence of 100 μM dopamine (open bars), 50 μM glutamate (striped bars), and a mixture of 100 μM dopamine and 50 μM glutamate (filled bars). SCH23390 (5 μM) and spiperone (5 μM) were added to the culture media 30 min before addition of dopamine and glutamate as indicated. Preincubation with SCH23390 or a mixture of SCH23390 and spiperone resulted in significant (***p < 0.05) reduction of cell death in YAC128 MSNs. Preincubation with spiperone alone had no statistically significant effect on YAC128 MSN apoptosis (ns). B, D₁-class DAR agonist SKF38393 promotes glutamate-induced apoptosis in YAC128 MSNs. The fraction of TUNEL-positive nuclei is shown for WT and YAC128 MSNs incubated for 8 h in the presence of DAR agonists (open bars; either 25 μM SKF38393 or 25 μM quinpirole), 50 μM glutamate (striped bars), and a mixture of DAR agonist and 50 μM glutamate (filled bars). Incubation with a mixture of SKF38393 and glutamate resulted in a significant (***p < 0.05) increase in cell death in YAC128 MSNs, whereas (−)-quinpirole had no statistically significant effect on YAC128 MSN apoptosis (ns). The apoptosis of WT MSNs was not affected. C, Inhibition of mGluR1/5 and NMDAR protects YAC128 MSNs from dopamine/glutamate-induced apoptosis. Identical experiments as described in A were performed in the presence of 20 μM MPEP and 50 μM CPCCOEt or 10 μM (+)-MK801. The inhibitors were added to the culture media 30 min before addition of dopamine and glutamate as indicated. Preincubation with MPEP/CPCCOEt or (+)-MK801 significantly (***p < 0.05) protected YAC128 MSNs from dopamine/glutamate mixture-induced cell death. D, Inhibition of NR2B NMDA receptors and InsP₃R protects YAC128 MSNs from dopamine/glutamate-induced apoptosis. Identical experiments as described in A were performed in the presence of 10 μM ifenprodil, 400 μM 2-APB, or 200 μg/ml enoxaparin. Ifenprodil was added 30 min before addition of dopamine and/or glutamate, and 2-APB and enoxaparin were added 2–3 h in advance. Preincubation with ifenprodil, 2-APB, and enoxaparin significantly (***p < 0.05) protected YAC128 MSNs from dopamine/glutamate-induced cell death. A–D, Four to six microscopic fields (200 –300 MSNs each) were counted for each experimental condition.