DNA was extracted from peripheral blood. Within the MAOA promoter there is a 30-bp repeated sequence present in 2, 3, 3.5, 4, or 5 copies. This polymorphism was amplified from 25ng genomic DNA using the following primer sequences: Forward 5′ CCC AGG CTG CTC CAG AAA C 3′ and reverse 5′ ACT CAG AAC GGA TGC TCC ATT CG 3′. Because of the high GC content around the repeat region, amplifications were performed using Invitrogen's PlatinumTaq and PCRX Enhancer System kits, according to the manufacturer's protocol (Invitrogen, Carlsbad, California), in a total reaction volume of 25 μl. Amplifications were performed on a Perkin Elmer 9700 thermocycler (Applied Biosystems, Foster City, CA) with one cycle at 96°C for 10 min followed by 30 cycles of 94°C for 15 sec, 60°C for 15 sec, 72°C for 30 sec, and a final 3-minute extension at 72°C. The forward primer was labeled with the fluorescent dye 6-FAM, and amplicons were visualized on an ABI 3100 capillary sequencer. Allele sizes (allele 2, 233 bp; allele 3, 263 bp; allele 3.5, 278 bp; allele 4, 293
