ACTIVATION OF GABAA RECEPTORS AND INHIBITION OF NEUROSTEROID SYNTHESIS HAVE SEPARABLE ESTROUS-DEPENDENT EFFECTS ON BINGE DRINKING IN FEMALE MICE

poster abstractAlcohol concentrations relevant to the beginning stages of binge intoxica-tion may selectively activate GABAA receptor subtypes expressing δ-subunit proteins (δ-GABAAR). Indeed, administration of agonists that interact with these δ-GABAAR prior to alcohol access, can abolish binge drinking behavior (Melon and Boehm, 2011). Unfortunately, our ability to manipulate binge drinking in females is dependent upon estrous phase. The present experi-ments were designed to clarify the estrous-dependent effects of activation of δ-GABAAR on binge drinking. Specifically, we were interested in demonstrat-ing whether females display more persistent binge drinking as a function of cycle-dependent changes in the synthesis of endogenous neurosteroids that modulate δ-GABAAR. Using the Drinking-in-the-Dark binge-drinking model, regularly cycling female mice were given 2 hours of daily access to alcohol (20%v/v). Vaginal cytology was assessed after each drinking session to track estrous status. In experiment 1, animals were administered gaboxadol (an agonist with high affinity for δ-GABAAR) prior to their 8th day of access. In experiment 2, these methods were repeated, but mice received vehicle or finasteride (a neurosteroid synthesis inhibitor) 22hr prior to their 8th day of access. Results from experiment 1 demonstrated that diestrus females were insensitive to the significant gaboxadol-induced decrease in binge drinking observed for proestrus, estrus and metestrus females. In experiment 2, ve-hicle and finasteride treated diestrus females exhibited gaboxadol-induced reduction of their binge drinking. Surprisingly, finasteride pretreatment sig-nificantly reduced binge drinking for estrus females. These studies suggest that ovarian-linked changes to extrasynaptic GABAA R and to neurosteroid activity may be important factors in the binge consumption of alcohol for females. Future studies will further explore the role that acute stress during diestrus may play in inhibiting the effects of δ-GABAA R activation on binge drinking

A Novel, Synthetic, Neuroactive Steroid Is Effective at Decreasing Depression-Like Behaviors and Improving Maternal Care in Preclinical Models of Postpartum Depression

Preclinical testing of treatments for postpartum depression (PPD) has been limited due to the lack of available animal models of such a complex disorder. To address this limitation, our laboratory has generated unique preclinical mouse models that exhibit abnormal postpartum behaviors. Mice with a loss or reduction in the expression of the GABAA receptor (GABAAR) δ subunit (Gabrd−/− or Gabrd+/−, respectively) and mice that lack the K+/Cl− co-transporter, KCC2, specifically in corticotropin-releasing hormone (CRH) neurons (KCC2/Crh mice) exhibit depression-like behaviors restricted to the postpartum period and deficits in maternal care, which serve as useful tools for testing novel therapeutic compounds. Utilizing these preclinical models, we tested the ability of a novel, synthetic, neuroactive steroid developed by SAGE Therapeutics, SGE-516, to improve abnormal postpartum behaviors. Gabrd−/−, Gabrd+/−, and KCC2/Crh dams treated with SGE-516 (450 mg/kg chow) during late pregnancy exhibit a decrease in depression-like behaviors and improvements in maternal care at 48 h postpartum. Interestingly, acute treatment with SGE-516 also exhibits robust therapeutic effects in these preclinical PPD models. We previously discovered abnormal stress reactivity associated with hypothalamic-pituitary-adrenal (HPA) axis dysregulation associated with depression-like behaviors in the preclinical PPD models, evident from an increase in stress-induced corticosterone levels and dephosphorylation and downregulation of KCC2 in the paraventricular nucleus of the hypothalamus (PVN) during the peripartum period. Here we demonstrated that SGE-516 treatment is sufficient to prevent the stress-induced increase in corticosterone and dephosphorylation and downregulation of KCC2 in the PVN. In contrast, and consistent with the distinct pharmacology of SGE-516 compared to benzodiazepines, treatment with clobazam (250 mg/kg chow) did not alter the depression-like phenotype or deficits in maternal care observed in these preclinical models of PPD. These findings are consistent with the positive double-blind, randomized, placebo-controlled trial findings of a similar compound, brexanolone, in the treatment of patients with postpartum depression. Further, these findings validate the use of these preclinical models of PPD for screening novel compounds for the treatment of postpartum depression

Activation of extrasynaptic δ-GABAA receptors globally or within the posterior-VTA has estrous-dependent effects on consumption of alcohol and estrous-independent effects on locomotion

Recent reports support higher than expected rates of binge alcohol consumption among women and girls. Unfortunately, few studies have assessed the mechanisms underlying this pattern of intake in females. Studies in males suggest that alcohol concentrations relevant to the beginning stages of binge intoxication may selectively target tonic GABAergic inhibition mediated by GABAA receptor subtypes expressing the δ-subunit protein (δ-GABAARs). Indeed, administration of agonists that interact with these δ-GABAARs prior to alcohol access can abolish binge drinking behavior in male mice. These δ-GABAARs have also been shown to exhibit estrous-dependent plasticity in regions relevant to drug taking behavior, like the hippocampus and periaqueductal gray. The present experiments were designed to determine whether the estrous cycle would alter binge drinking, or our ability to modulate this pattern of alcohol use with THIP, an agonist with high selectivity and efficacy at δ-GABAARs. Using the Drinking-in-the-Dark (DID) binge-drinking model, regularly cycling female mice were given 2h of daily access to alcohol (20%v/v). Vaginal cytology or vaginal impedance was assessed after drinking sessions to track estrous status. There was no fluctuation in binge drinking associated with the estrous cycle. Both Intra-posterior-VTA administration of THIP and systemic administration of the drug was also associated with an estrous cycle dependent reduction in drinking behavior. Pre-treatment with finasteride to inhibit synthesis of 5α-reduced neurosteroids did not disrupt THIP's effects. Analysis of δ-subunit mRNA from posterior-VTA enriched tissue samples revealed that expression of this GABAA receptor subunit is elevated during diestrus in this region. Taken together, these studies demonstrate that δGABAARs in the VTA are an important target for binge drinking in females and confirm that the estrous cycle is an important moderator of the pharmacology of this GABAA receptor subtype