Inhibitory effects of cilnidipine on peripheral and brain N-type Ca2+ channels expressed in BHK cells.
We investigated differences in electrophysiological characteristics between peripheral and central N-type Ca(2+) channels, containing alpha(1B-a) and a(1B-c), respectively. In addition, we examined the inhibitory effects of cilnidipine, a dihydropyridine (DHP) derivative, on both channels. Both alpha(1B) subunits were transiently expressed in BHK cells, and then analyzed using the whole-cell patch-clamp technique. The current-voltage relationship showed that alpha(1B-c) currents were activated at more negative potentials than alpha(1B-a) currents. The voltage-dependent steady-state inactivation and activation showed that the V(1/2) values for inactivation and activation of alpha(1B-c) (-88.5+/-1.3 and -33.2+/-1.3 mV) were both significantly more negative than those for alpha(1B-a) (-83.3+/-1.3 and -27.9+/-2.3 mV). Despite the different electrophysiological characteristics of these two N-type channels, cilnidipine blocked both with similar potency within the range 0.1 to 10 microM. Furthermore, cilnidipine had no effect on the I-V relationships or the steady-state inactivation curves. Our data indicate that the spliced positions of alpha(1B-a) and a(1B-c) may affect not only their voltage-sensing abilities but also the kinetics of channel activation and inactivation. The data also suggest that cilnidipine binds to sites independent of those controlling voltage-sensing and channel kinetics in these alpha(1B) subunits.
Kato
Kenichi
K
Department of Cell Physiology and Molecular Biology, Fukuoka Dental College, Fukuoka 814-0193, Japan. kenkato@college.fdcnet.ac.jp
Wakamori
Minoru
M
Mori
Yasuo
Y
Imoto
Keiji
K
Kitamura
Kenji
K
D000818:Animals; D001921:Brain / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020864:Calcium Channels, N-Type / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D006224:Cricetinae; D004095:Dihydropyridines / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D010525:Peripheral Nerves / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D014162:Transfection
D002121:Calcium Channel Blockers; D020864:Calcium Channels, N-Type; D004095:Dihydropyridines; C065927:cilnidipine