PROPERTIES OF BA2-1E AND ALPHA-1E-BETA-3 CONSTRUCTS EXPRESSED IN HEK293 CELLS - PHYSIOLOGY, PHARMACOLOGY, AND COMPARISON TO NATIVE T-TYPE BA2+ CURRENTS( CURRENTS ARISING FROM HUMAN ALPHA)

Currents arising from human alpha 1E and alpha 1E beta 3 Ca2+ channel subunits expressed in HEK-293 cells were examined with whole-cell reco rding methods and compared to properties of T-current in DRG neurons s tudied under identical ionic conditions. Coexpression of alpha 1E subu nit with the beta 3 subunit shifted activation to more negative potent ials. Activation and deactivation of both variants were comparable at most voltages, with deactivation becoming faster, but less voltage-dep endent, at more negative potentials. The inactivation time course for alpha 1E and alpha 1E beta 3 currents was best described by at least t wo exponential components. Recovery from inactivation was markedly vol tage-dependent and similar for both constructs. In comparison to alpha 1E and alpha 1E beta 3 constructs, T current activation was shifted t o more negative potentials, activation was typically slower, deactivat ion exhibited a steeper voltage-dependence, and recovery from inactiva tion was less voltage-dependent. Over most of the activation range, na tive T current inactivated more completely and in a single exponential fashion. Despite some pharmacological similarities (e.g. octanol, bar biturates) between alpha 1E and T-type currents, aspects of blockade b y amiloride and phenytoin appear to distinguish alpha 1E current from T-type currents. The results define several distinguishing features of alpha 1E currents that distinguish them from native T-type currents. (C) 1998 Elsevier Science Ltd. All rights reserved.