Rats were injected intraperitoneally thrice weekly for 4 weeks with doses of selective inhibitors of monoamine oxidase type A (clorgyline, 1 mg/kg) or B ((-)-selegiline, 10 mg/kg), or saline. Both treatments produced sustained elevations of concentrations of dopamine and serotonin, and decreased their deaminated metabolites in forebrain tissue. Nevertheless, no change in binding of [H-3]GBR-12935 to the dopamine transporter or of [H-3]paroxetine to the serotonin transporter in caudate-putamen or nucleus accumbens septi was found with quantitative autoradiography. These results support the impression that transporter proteins for these monoamines are not regulated by increased ligand abundance. (C) 1997 Elsevier Science Ireland Ltd.