Purpose of the assay is to determine the functionality of the SLC7A3 transporter, stably expressed in the HEK-293 JumpIn TREx cell line (SLC7A3 OverExpressing - OE - cell line). SLC7A3 (CAT-3) mediates the entry of L-type cationic amino acids (i.e., L-Arginine, L-Ornithine and L-Lysine) into neurons. The transport mediated by SLC7A3 is therefore electrogenic. For this reason, the HEK-293 JumpIn TREx/SLC7A3 OE cell line was tested using the Membrane Potential (MP) dye read-out, which is described in the section below.