Targeted Inhibition of Upregulated Sodium-Calcium Exchanger in Rat Inferior Colliculus Suppresses Alcohol Withdrawal Seizures

Abstract

The inferior colliculus (IC) is critical in initiating acoustically evoked alcohol withdrawal-induced seizures (AWSs). Recently, we reported that systemic inhibition of Ca²⁺ entry via the reverse mode activity of the Na⁺/Ca²⁺ exchanger (NCX_rev) suppressed AWSs, suggesting remodeling of NCX expression and function, at least in the IC, the site of AWS initiation. Here, we probe putative changes in protein expression in the IC of NCX isoforms, including NCX type 1 (NCX1), 2 (NCX2), and 3 (NCX3). We also evaluated the efficacy of targeted inhibition of NCX1_rev and NCX3_rev activity in the IC on the occurrence and severity of AWSs using SN-6 and KB-R943, respectively. We used our well-characterized alcohol intoxication/withdrawal model associated with enhanced AWS susceptibility. IC tissues from the alcohol-treated group were collected 3 h (before the onset of AWS susceptibility), 24 h (when AWS susceptibility is maximal), and 48 h (when AWS susceptibility is resolved) following alcohol withdrawal; in comparison, IC tissues from the control-treated group were collected at 24 h after the last gavage. Analysis shows that NCX1 protein levels were markedly higher 3 and 24 h following alcohol withdrawal. However, NCX3 protein levels were only higher 3 h following alcohol withdrawal. The analysis also reveals that bilateral microinjections of SN-6 (but not KB-R7943) within the IC markedly suppressed the occurrence and severity of AWSs. Together, these findings indicate that NCX1 is a novel molecular target that may play an essential role in the pathogenesis and pathophysiology of AWSs.

Keywords: Calcium signaling; Generalized tonic–clonic seizures; KB-R7943; Protein expression; SN-6.