Sex differences in acoustic startle responses and seizure thresholds between ethanol-withdrawn male and female rats.

AIMS: We have found consistent and significant sex differences in recovery from the increased seizure susceptibility observed during ethanol withdrawal (EW) in our rat model system. The main objective of the present study was to determine if sex differences in EW generalized to an additional behavioral measure startle reactivity. METHODS: Acoustic startle or seizure threshold responses were measured in separate groups of rats at 1 day or 3 days of EW. RESULTS: Both pair-fed control and EW males showed greater increases in acoustic startle responses than either the female or ovariectomized female (OVX) counterparts. There was a selective effect of pregnanolone on acoustic startle in that it reduced peak force of response only at 3 days EW in male rats. Unexpectedly, it modestly increased startle reactivity in control female and OVX rats. Acute treatment with low-dose ethanol trended toward reducing startle responses in control animals, as expected, while generally enhancing startle responses during EW. All sex conditions showed an enhanced startle response during EW following administration of the higher dose of estradiol compared to control animals. Estradiol did not alter seizure thresholds in control animals. However, it was anticonvulsant for males at 3 days EW, females and OVX at 1 day EW. CONCLUSIONS: Observed sex differences in the startle reactivity during EW were consistent with earlier findings comparing EW seizure risk in male and female rats. Responses of OVX suggested that both hormones and differences in brain structures between males and females have a role in these sex differences. Our findings add weight to recommendations that treatment of alcohol withdrawal in humans should consider hormonal status as well as withdrawal time.

Influence of hormonal status on behavioral responses to an acute ethanol challenge during ethanol withdrawal in male and female rats.

We previously reported significant sex differences in ethanol withdrawal (EW) recovery as well as in sensitivity to GABA(A) receptor modulators during EW. The aim of the present study was to determine if hormonal status moderated behavioral responses to an acute ethanol challenge in EW animals comparing two different behaviors. An initial set of experiments explored motor-incoordinating effects of the acute ethanol injection during EW at either 1 day or 3 days of withdrawal. EW male, but not female, rats showed a decrease in coordination compared to controls that persisted through 3 days EW. Female rats displayed tolerance to the motor-incoordinating actions of the acute ethanol challenge at 1 day EW whereas tolerance was more evident in EW male rats at 3 days. In contrast, EW animals generally remained responsive to the anticonvulsant actions of ethanol, irrespective of hormonal status. While EW by itself did not significantly alter seizure latency, duration or severity, it increased seizure-induced mortality especially at 3 days EW. There was some evidence of tolerance to the anticonvulsant effect of the acute ethanol challenge at the lowest dose employed (0.62 g/kg), which varied by sex condition and time of EW. All sex conditions displayed marked sensitivity to the anticonvulsant effects of the ethanol challenge at the two higher doses studied. Overall, ovariectomized females showed the greatest response to the acute ethanol administration. These findings provide additional evidence of a divergence in behavioral responses during EW and suggest that multiple neuroadaptations moderate various responses to ethanol during EW, with minor contributions of hormonal status.