Up-regulation of L-type high voltage-gated calcium channel subunits by sustained exposure to 1,4- and 1,5-benzodiazepines in cerebrocortical neurons

Abstract

The aim of this study is to examine how sustained exposure to two 1,4-benzodiazepines (BZDs) with different action period, diazepam and brotizolam, and a 1,5-BZD, clobazam, affects L-type high voltage-gated calcium channel (HVCC) functions and its mechanisms using primary cultures of mouse cerebral cortical neurons. The sustained exposure to these three BZDs increased [45Ca2+] influx, which was due to the enhanced [ 45Ca2+] entry through L-type HVCCs but not through of Cav2.1 and Cav2.2. Increase in [3H]diltiazem binding after the exposure to these three BZDs was due to the increase in the binding sites of [3H]diltiazem. Western blot analysis showed increase of Cav1.2 and Cav1.3 in association with the increased expression of α2/δ1 subunit. Similar changes in [3H]diltiazem binding and L-type HVCC subunit expression were found in the cerebral cortex from mouse with BZD physical dependence. These results indicate that BZDs examined here have the potential to increase L-type HVCC functions mediated via the enhanced expression of not only Cav1.2 and Cav1.3 but also α2/δ1 subunit after their sustained exposure, which may participate in the development of physical dependence by these BZDs. © 2007 The Authors.