Decreased anticonvulsant efficacy of allopregnanolone during ethanol withdrawal in female Withdrawal Seizure-Prone vs. Withdrawal Seizure-Resistant mice

Abstract

SUMMARYThe GABAergic neurosteroid allopregnanolone (ALLO) has been repeatedly shown to have an increased anticonvulsant effect during ethanol withdrawal in rats and in C57BL/6J mice. In contrast, the seizure prone DBA/2J inbred strain and the Withdrawal Seizure-Prone (WSP) selected line exhibited decreased sensitivity to ALLO's anticonvulsant effect during ethanol withdrawal, with no change in sensitivity in the Withdrawal Seizure-Resistant (WSR) line. To date, only male mice have been tested. Thus, the present study examined ALLO sensitivity during ethanol withdrawal in female WSP and WSR mice, since females display less severe physical symptoms of withdrawal and have higher circulating ALLO levels than males. Female WSP and WSR mice were exposed to ethanol vapor or air for 72 hr. During peak ethanol withdrawal, separate groups of mice were injected with vehicle or ALLO (0, 3.2, 10, or 17 mg/kg, ip) prior to the timed tail vein infusion of pentylenetetrazol (PTZ). ALLO injection significantly increased the threshold dose for onset to PTZ-induced convulsions, indicating an anticonvulsant effect, in female WSP and WSR mice. During ethanol withdrawal, sensitivity to ALLO's anticonvulsant effect was slightly increased in female WSR mice but was significantly decreased in female WSP mice. This line difference in sensitivity to ALLO during ethanol withdrawal in female mice was similar to that in the male mice. Notably, all seizure prone genotypes tested to date displayed tolerance to the anticonvulsant effect of ALLO during ethanol withdrawal, suggesting that decreased sensitivity of GABA A receptors to ALLO may contribute to the increased ethanol withdrawal phenotype.

Selected Line Difference in the Effects of Ethanol Dependence and Withdrawal on Allopregnanolone Levels and 5α‐Reductase Enzyme Activity and Expression

“…In animals that exhibit mild withdrawal, sensitivity to the anticonvulsant effect of alphaxalone, pregnanolone or ALLO was enhanced in rats (Alele and Devaud, 2007; Cagetti et al, 2004; Devaud et al, 1996) or C57BL/6J mice (Finn et al, 2000). Either enhancement or no change in sensitivity to the anticonvulsant effect of ALLO was observed in female and male WSR mice, respectively (Beckley et al, 2008; Finn et al, 2006b). Thus, it is likely that in seizure-prone versus -resistant genotypes, there is a balance between the alterations of concentrations of ALLO at GABA A receptors and the concomitant change in GABA A receptor sensitivity to ALLO during the ethanol withdrawal phase (as discussed in Finn et al, 2004), with a similar relationship for CORT at glucocorticoid and/or mineralocorticoid receptors.…”

Manipulation of GABAergic steroids: Sex differences in the effects on alcohol drinking- and withdrawal-related behaviors

“…Although not identical, this finding is consistent with the enhanced sensitivity to ALLO's anticonvulsant effect in female versus male rats (Devaud et al, 1996). In contrast, female WSP mice exhibited cross-tolerance to the anticonvulsant effect of ALLO during ethanol withdrawal (Figure 5B; Beckley et al, 2008). Male WSP mice also exhibited cross-tolerance to the anticonvulsant effect of ALLO during ethanol withdrawal, and this decrease in behavioral sensitivity corresponded to a right-ward shift in the functional sensitivity of GABA A receptors to ALLO during withdrawal (Figure 5A; Finn et al, 2006b).…”

“…In the WSP and WSR selected lines, female and male WSR mice from the replicate-1 line exhibited sensitization to ALLO's anticonvulsant effect during ethanol withdrawal (Figure 5C & 5D; Beckley et al, 2008). However, when data were collapsed across both replicates of the WSR line, sensitivity to the anticonvulsant effect of ALLO was unchanged in male WSR mice (Finn et al, 2006b).…”

“…Values represent the mean (± SEM) for the number of animals in parentheses. Data (from replicate-1 animals) were adapted from previously published data (Beckley et al, 2008; Finn et al, 2006b). …”

Ethanol withdrawal-induced dysregulation of neurosteroid levels in plasma, cortex, and hippocampus in genetic animal models of high and low withdrawal

“…Both WSP and DBA mice exhibit high WD severity, measured by increased handling-induced convulsions (HICs) and anxiety following 72 h of continuous ethanol vapor or CIE vapor (Crabbe et al, 1985; Crabbe, 1998; Finn and Crabbe, 1999; Finn et al, 2004; Gorin et al, 2005; Kosobud and Crabbe, 1986; McCool and Chappell, 2015; Metten and Crabbe, 2005; Metten et al, 2010). Importantly, both WSP and DBA mice exhibited tolerance to ALLO’s anticonvulsant effect during peak (8 h) WD (Beckley et al, 2008; Finn et al, 2000, 2004, 2006), and this tolerance in WSP mice also corresponded to a reduction in functional sensitivity of GABA A Rs to ALLO (Finn et al, 2006) and reduced anticonvulsant effect of intra-CA1 ALLO (Gililland-Kaufman et al, 2008). Thus, a reduction in GABA A R sensitivity to neurosteroids may contribute to a severe WD phenotype in genetic animal models of high WD.…”