Relative levels of 3R and 4R tau mRNAs were determined by RT-PCR using the primer sets: forward 5′-AAGTCGCCGTCTTCCGCCAAG-3′; reverse 5′-GTCCAGGGACCCAATCTTCGA-3′ as previously described30. The PCR amplification was performed in a final volume of 20 μl under the following conditions: 95°C for 15 min, and then 30 cycles of at 94°C for 30 seconds, 60°C for 30 seconds, 74°C for 90 seconds with a final 10 min extension at 15 min at 95°C. RT-PCR products were analyzed on 2% agarose gel: 4R tau, 381 bp; 3R tau 288 bp.
