Increase in Expression of α1 and α2/δ1 Subunits of L-Type High Voltage-Gated Calcium Channels After Sustained Ethanol Exposure in Cerebral Cortical Neurons

Abstract

Abstract. Previous reports revealed up-regulation of L-type high voltage-gated calcium channels (HVCCs) in mouse brains with ethanol physical dependence. We investigated mechanisms of enhancement of L-type HVCC function using mouse cerebrocortical neurons exposed to 50 mM ethanol for 3 days and the brains of mouse physically dependent on ethanol. Ethanol facilitated 30 mM KCl-stimulated 45 Ca 2+ influx in dose-and duration-dependent manners, which was abolished by nifedipine, an inhibitor specific to L-type HVCCs, but not by inhibitors for other types of HVCCs. Increase in [3 H]PN200-110 binding to the particulate fractions from the ethanol-treated neurons was due to increased B max value with no changes in K d value. Western blot analysis showed the increased expression of α1C, α1D, and α2/ δ1 subunits with decreased β4 subunit expression and no changes in expressions of α1A, α1B, α1F, and α2 subunits. A similar pattern of the changes in the expression of these subunits of L-type HVCCs were observed in the cerebral cortex from mouse with ethanol physical dependence. These results indicate that sustained ethanol exposure to the neurons induces up-regulation of L-type HVCCs, which is due to increased expressions of α1C, α1D, and α2 / δ1 subunits, and produces no alterations in P / Q-and N-type HVCC functions.

Inhibition of Recombinant L-Type Voltage-Gated Calcium Channels by Positive Allosteric Modulators of GABAA Receptors

“…It is noteworthy that long-term treatment with BDZs, barbiturates, and ethanol increases neuronal Ca 2ϩ influx in vitro and in vivo, possibly through L-VGCCs Rabbani and Little, 1999;Katsura et al, 2006Katsura et al, , 2007Xiang et al, 2008). An upregulation of L-VGCC function during long-term treat-ment with the various GABA A R modulators is implicated in contributing to withdrawal hyperexcitability (Dolin et al, 1987;Rabbani and Little, 1999;Xiang and Tietz, 2007;Xiang et al, 2008).…”

Regional Differences of L-type High Voltage-Gated Calcium Channel Subunit Expression in the Mouse Brain After Chronic Morphine Treatment

“…The previous investigations reveal that β subunits facilitate Ca 2+ currents via modification of inactivation kinetics of channel interaction with second messenger regulation (33 -35). Similarly, the decreases of β4 subunit in the cerebral cortex after chronic treatment with ethanol (10) and in primary cultures of cerebral cortical neurons continuously exposed to ethanol and morphine (25,29) were reported. However, the pathophysiological roles of the decrease of β4 subunit levels observed in the cerebral cortex from mice with morphine physical dependence remain to be elucidated at present.…”

“…In addition, the up-regulation of L-type HVCC subunits similar to that observed in the cerebral cortex from animals with physical dependence on ethanol and nicotine occurs in neuronal cells continuously exposed to ethanol and nicotine as well as morphine (17,25,28,29). The previously reported observations and the present data obtained by the radiolabeled dihydropyridine binding assay and immunoblot analysis for L-type HVCC subunits indicate that the up- regulation of α1C and α1D of L-type HVCCs and the α2/ δ1 subunit play important roles in the development of physical dependence on morphine as well as ethanol and nicotine.…”

Alcohol usage and abrupt cessation modulate diurnal activity

“…Furthermore, ethanol has been shown to upregulate long-lasting (L-type) calcium channels (14). L-type calcium channels are primarily found on dendrites and neuronal cell bodies in the brain (17).…”