Methamphetamine (METH) causes release of stored intracellular dopamine (DA). We explored the interactions of METH with the recombinant human vesicular monoamine (hVMAT2) and/or human DA transporters (hDAT) in transfected mammalian (HEK293) cells and compared the findings with those for DA. In 'static' release assays at 37°C, less than 20% of pre-loaded [3H]DA was lost after 60 min, while nearly 80% of pre-loaded [3H]METH was lost at 37°C under non-stimulated conditions. Results obtained by measuring substrate release using a superfusion apparatus revealed an even greater difference in substrate efflux. At pH 7.4, nearly all of the pre-loaded [3H]METH was lost after just 6 min, compared with the loss of 70-80% of pre-loaded [ 3H]DA (depending on cell type) after superfusion for 32 min. Increasing the extracellular pH from 7.4 to 8.6 had opposite effects on [ 3H]DA and [3H]METH retention. At pH 8.6, [ 3H]METH was retained more effectively by both hDAT and hDAT-hVMAT2 cells, compared with results obtained at extracellular pH 7.4. [ 3H]DA, however, was more effectively retained at pH 7.4 than at pH 8.6. These data suggest that DA and METH interact differently with the DAT and VMAT2, and require different H+ concentrations to exert their effects.
- Dopamine transporter
- Vesicular transporter
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience