PROGESTERONE AS A NEUROSTEROID - ACTIONS WITHIN THE NERVOUS-SYSTEM

1. Some progesterone is synthesized within both the central and the pe ripheral nervous systems, where it regulates neurotransmission and imp ortant glial functions, such as the formation of myelin, Progesterone can thus be designated a ''neurosteroid.'' 2. Steroids act not only on the brain, but also on peripheral nerves, which offer many advantages to study the biological significance of locally produced neurosteroid s: their remarkable plasticity and relatively simple structure. 3. By using the regenerating mouse sciatic nerve as a model, we have shown t hat progesterone synthesized by rat Schwann cells promotes the formati on of new myelin sheaths, Progesterone also increases the number of my elinated axons when added at a low concentration to cocultures of Schw ann cells and sensory neurons. 4. These findings show a function on my elination for locally produced progesterone and suggest a new pharmaco logical approach of myelin repair.