Fetal ethanol effects on benzodiazepine sensitivity measured by behavior on the elevated plus-maze

Rodents prenatally exposed to ethanol demonstrate altered behavioral and hormonal responses to stressful environments. Prenatal ethanol exposure may also have long-term effects on the offspring's GABAergic system. Using the elevated plus-maze, the present study examined the sensitivity of adult Sprague-Dawley rat offspring from prenatal ethanol (E), pair-fed (PF) and ad lib-fed control (C) conditions to the effects of benzodiazepine (BZD) on plus-maze behavior and corticosterone (CORT) responses. At 60-90 days of age, E, PF, and C males and females were injected subcutaneously with either BZD or saline. Twenty minutes later animals were placed in an open field (OF) for a 5-min test and then on the plus-maze for a 5 min test; behaviors were recorded during testing and blood samples collected at the end of testing for CORT determinations. Overall, sex differences were observed in both OF and plus-maze behaviors. Females showed more ambulation and rearing in the OF than males, and exhibited increased exploratory behaviors and decreased fear-related behaviors compared to males an the plus-maze. Following BZD treatment, both males and females exhibited increased time on open arms, increased open arm entries, and decreased time on closed arms compared to saline-treated males and females, regardless of prenatal treatment. These differences did not appear to be due to altered activity levels, as BZD treatment had no effect on total ambulation in the OF. Importantly, although no significant differences in plus-maze behaviors were found among saline-injected E, PF, and C males or females, BZD treatment differentially affected E males and females compared to their PF and C counterparts. Both E males and females treated with BZD spent increased time on open arms and decreased time on closed arms compared to their PF and C counterparts, suggesting decreased fear. Further, BZD-treated E males exhibited decreased open and closed arm entries, spent significantly more time in the central area, and had lower CORT levels, another index of fear or stress, compared to BZD-treated PF and C males. These data support and extend previous work demonstrating that the plus-maze provides a reliable measure of anxiety/fear, and that plus-maze behavior is sensitive to anxiolytic agents such as BZD. Furthermore, these data suggest that prenatal ethanol exposure may alter sensitivity to the effects of BZD on plus-maze behavior and CORT responsiveness, and may do so differentially in male and females offspring. (C) 1998 Elsevier Science Inc.