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Figure 2 (A) Representative RT-PCR reactions at 35 cycles (Cyc) and 40 cycles, respectively. The control primers (GAPDH ([G]) have multiple bands due to the different optimal annealing temperatures of the GAPDH primers compared with the opioid-receptor subtypes. The µ and receptor PCR products are shown at the different cycle lengths. The receptor nested PCR data are not shown. (B) This histogram demonstrates the relative intensities (expressed in arbitrary units [AU]) of the PCR products of the opioid receptor subtypes in both human atrial and ventricular tissue. The AU for the µ and receptor subtypes reflect the mean PCR product generated after 40 cycles of PCR, and the AU for the receptor reflects the PCR products after the second round of nested PCR. bp = base pair; MRNA = messenger RNA; PCR = polymerase chain reaction.