For electrophysiological analysis cells were transfected with a BK variant (BKALCOREX, BK-STREX or BK-Insertless in pVAX) together with the expression plasmid (πH3-CD8) for the α subunit of the human CD8 lymphocyte surface antigen (GeneBank M12824), allowing for identification of transfected cells with CD-8 antibody-coated beads (Dynal/Invitrogen) as previously.