Brain and pineal 7α-hydroxypregnenolone stimulating locomotor activity: identification, mode of action and regulation of biosynthesis.

Biologically active steroids synthesized in the central and peripheral nervous systems are termed neurosteroids. However, the biosynthetic pathways leading to the formation of neurosteroids are still incompletely elucidated. 7a-Hydroxypregnenolone, a novel bioactive neurosteroid stimulating locomotor activity, has been recently identified in the brain of newts and quail. Subsequently, the mode of action and regulation of biosynthesis of 7a-hydroxypregnenolone have been determined. Moreover, recent studies on birds have demonstrated that the pineal gland, an endocrine organ located close to the brain, is an important site of production of neurosteroids de novo from cholesterol. 7a-Hydroxypregnenolone is a major pineal neurosteroid that stimulates locomotor activity in juvenile chickens, connecting lightinduced gene expression with locomotion. This review summarizes the advances in our understanding of the identification, mode of action and regulation of biosynthesis of brain and pineal 7a-hydroxypregnenolone, a potent stimulator of locomotor activity.