ZD 7288 inhibits T-type calcium current in rat hippocampal pyramidal cells

Many studies have used the channel blocker ZD 7288 to assess possible physiological and pathophysiological roles of hyperpolarization-activated cation currents (I(h)) in view of the known interplay between Ih and other membrane conductances, the effects in Wistar rats of ZD 7288 on low-voltage-activated (LVA (or T-type)) Ca2(+) channels were examined in whole-cell patch-clamp recordings from CA1 pyramidal cells in the presence of TTX, TEA, 4-AP, CsCl, BaCl(2) and nifedipine. ZD 7288 reduced T-type calcium channel currents and this effect was concentration dependant. ZD 7288 blocked T-type currents when applied extracellularly, but not when included in the recording pipette. Furthermore, ZD 7288 altered the steadystate voltage-dependent inactivation of T-currents. These results indicate that the blocker ZD 7288 has effects on voltage sensitive channels additional to those reported for the Ih current. (c) 2008 Elsevier Ireland Ltd. All rights reserved.