Brexanolone, a GABA _A Modulator, in the Treatment of Postpartum Depression in Adults: A Comprehensive Review

Endocrine factors are purported to play a role in the etiology of postpartum depression, but direct evidence for this role is lacking. The authors investigated the possible role of changes in gonadal steroid levels in postpartum depression by simulating two hormonal conditions related to pregnancy and parturition in euthymic women with and without a history of postpartum depression. The supraphysiologic gonadal steroid levels of pregnancy and withdrawal from these high levels to a hypogonadal state were simulated by inducing hypogonadism in euthymic women-eight with and eight without a history of postpartum depression-with the gonadotropin-releasing hormone agonist leuprolide acetate, adding back supraphysiologic doses of estradiol and progesterone for 8 weeks, and then withdrawing both steroids under double-blind conditions. Outcome measures were daily symptom self-ratings and standardized subjective and objective cross-sectional mood rating scales. Five of the eight women with a history of postpartum depression (62.5%) and none of the eight women in the comparison group developed significant mood symptoms during the withdrawal period. Analysis of variance with repeated measures of daily and cross-sectional ratings of mood showed significant phase-by-group effects. These effects reflected significant increases in depressive symptoms in women with a history of postpartum depression but not in the comparison group after hormone withdrawal (and during the end of the hormone replacement phase), compared with baseline. The data provide direct evidence in support of the involvement of the reproductive hormones estrogen and progesterone in the development of postpartum depression in a subgroup of women. Further, they suggest that women with a history of postpartum depression are differentially sensitive to mood-destabilizing effects of gonadal steroids.

Fast inhibitory neurotransmission in the brain is principally mediated by the neurotransmitter γ-aminobutyric acid (GABA) and its synaptic target, the GABA-A receptor. Dysfunction of this receptor results in neurological disorders and mental illnesses including epilepsy, anxiety and insomnia. The GABA-A receptor is also a prolific target for therapeutic, illicit, and recreational drugs, including benzodiazepines, barbiturates, anesthetics and ethanol. We present high resolution cryo-electron microscopy structures of the human α1β2γ2 GABA-A receptor, the predominant isoform in the adult brain. The receptor is bound to GABA and the benzodiazepine site antagonist flumazenil, the first-line clinical treatment for benzodiazepine overdose. The receptor architecture reveals unique heteromeric interactions for this important class of inhibitory neurotransmitter receptors. This work provides a template for understanding receptor modulation by GABA and benzodiazepines, and will assist rational approaches to therapeutic targeting of this receptor for neurological disorders and mental illness.

Increasing evidence points to an association between major depressive disorders (MDDs) and diverse types of GABAergic deficits. In this review, we summarize clinical and preclinical evidence supporting a central and causal role of GABAergic deficits in the etiology of depressive disorders. Studies of depressed patients indicate that MDDs are accompanied by reduced brain concentration of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) and by alterations in the subunit composition of the principal receptors (GABA(A) receptors) mediating GABAergic inhibition. In addition, there is abundant evidence that suggests that GABA has a prominent role in the brain control of stress, the most important vulnerability factor in mood disorders. Furthermore, preclinical evidence suggests that currently used antidepressant drugs (ADs) designed to alter monoaminergic transmission and nonpharmacological therapies may ultimately act to counteract GABAergic deficits. In particular, GABAergic transmission has an important role in the control of hippocampal neurogenesis and neural maturation, which are now established as cellular substrates of most if not all antidepressant therapies. Finally, comparatively modest deficits in GABAergic transmission in GABA(A) receptor-deficient mice are sufficient to cause behavioral, cognitive, neuroanatomical and neuroendocrine phenotypes, as well as AD response characteristics expected of an animal model of MDD. The GABAergic hypothesis of MDD suggests that alterations in GABAergic transmission represent fundamentally important aspects of the etiological sequelae of MDDs that are reversed by monoaminergic AD action.