Brain Allopregnanolone Induces Marked Scratching Behavior in Diet-Induced Atopic Dermatitis Mouse Model

In a study from 2019, researchers investigated the role of allopregnanolone (ALLO), a neurosteroid produced in the brain, in inducing scratching behavior in a mouse model of diet-induced atopic dermatitis. They found that systemic administration of ALLO led to significant scratching in mice with atopic dermatitis but did not affect normal mice. The scratching behavior was triggered by ALLO when administered into the brain's ventricular system (intracisternally), implicating supraspinal mechanisms, and was modulated by activation of GABA type A receptors and inhibition of serotonin type 3 receptors. Additionally, the study showed that endogenous ALLO production, increased by acute ethanol administration, was associated with scratching, which could be suppressed by finasteride, an ALLO synthesis inhibitor. This research provided the first evidence that both exogenously administered and endogenously produced ALLO can induce scratching in atopic dermatitis, suggesting potential targets for treating itch in this condition.