Inhibition of recombinant Ca(v)3.1 (alpha(1G)) T-type calcium channels by the antipsychotic drug clozapine.
Low voltage-activated T-type calcium channels are involved in the regulation of the neuronal excitability, and could be subject to many antipsychotic drugs. The effects of clozapine, an atypical antipsychotic drug, on recombinant Ca(v)3.1 T-type calcium channels heterologously expressed in human embryonic kidney 293 cells were examined using whole-cell patch-clamp recordings. At a standard holding potential of -100 mV, clozapine inhibited Ca(v)3.1 currents with an IC(50) value of 23.7+/-1.3 microM in a use-dependent manner. However, 10 microM clozapine inhibited more than 50% of the Ca(v)3.1 currents in recordings at a more physiologically relevant holding potential of -75 mV. Clozapine caused a significant hyperpolarizing shift in the steady-state inactivation curve of the Ca(v)3.1 channels, which is presumably the main mechanism accounting for the inhibition of the Ca(v)3.1 currents. In addition, clozapine slowed Ca(v)3.1 deactivation and inactivation kinetics but not activation kinetics. Clozapine-induced changes in deactivation and inactivation rates of the Ca(v)3.1 channel gating would likely facilitate calcium influx via Ca(v)3.1 T-type calcium channels. Thus, clozapine may exert its therapeutic and/or side effects by altering cell's excitability and firing properties through actions on T-type calcium channels.
Life Sciences Research Division, Korea Institute of Science and Technology, 39-1 Hawolgok-Dong, Seongbuk-Gu, Seoul, 136-791, Republic of Korea.
Kee-Hyun
KH
Choi
Hyewhon
H
Rhim
D000818:Animals; D014150:Antipsychotic Agents / Q000009:adverse effects / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000009:adverse effects / Q000494:pharmacology*; D020747:Calcium Channels, T-Type / Q000378:metabolism*; D002460:Cell Line; D003024:Clozapine / Q000009:adverse effects / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D007700:Kinetics; D009474:Neurons / Q000166:cytology / Q000187:drug effects; D018408:Patch-Clamp Techniques; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism
D014150:Antipsychotic Agents; C121855:CACNA1G protein, human; D002121:Calcium Channel Blockers; D020747:Calcium Channels, T-Type; D011994:Recombinant Proteins; D003024:Clozapine