Relationship between Cmax of MDMA, MDA, HHMA, or HMMA and cortical 5-HT depletion. Rats received a single oral dose of MDMA (20 mg/kg). One week later, cortical 5-HT levels were determined. The figures reflect within-subject analyses, as drug plasma levels and cortical 5-HT levels were measured in the same animal (n = 24). R (Pearson correlation coefficient) and p values are shown.