Alcohol withdrawal upregulates mRNA encoding for CaV2.1-α1 subunit in the rat inferior colliculus.

Abstract

We previously reported increased current density through P-type voltage-gated Ca2+ channels in inferior colliculus (IC) neurons during alcohol withdrawal. However, the molecular correlate of this increased P-type channel current is currently unknown. Here, we probe changes in mRNA and protein expression of the pore-forming CaV2.1-α1 (P/Q-type) subunits in IC neurons during the course of alcohol withdrawal-induced seizures (AWSs). Rats received three daily doses of ethanol or the vehicle every 8h for 4 consecutive days. The IC was dissected at various time intervals following alcohol withdrawal, and the mRNA and protein levels of the CaV2.1-α1 subunits were measured. In separate experiments, rats were tested for acoustically evoked seizure susceptibility 3, 24, and 48h after alcohol withdrawal. AWSs were observed 24h after withdrawal; no seizures were observed at 3 or 48h or in the control-treated rats. Compared to control-treated rats, the mRNA levels of the CaV2.1-α1 subunit were increased 1.9-fold and 2.1-fold at 3 and 24h, respectively; change in mRNA expression was nonsignificant at 48h following alcohol withdrawal. Western blot analyses revealed that protein levels of the CaV2.1-α1 subunits were not altered in IC neurons following alcohol withdrawal. We conclude that expression of the Cacna1a mRNA increased before the onset of AWS susceptibility, suggesting that altered CaV2.1 channel expression may play a role in AWS pathogenesis.