Evidence that 5α-pregnan-3α-ol-20-one is the metabolite responsible for progesterone anesthesia

Tadpoles (Rana catesbeiana) were anesthetized with [³H]-progesterone (PG) in order to identify the steroid responsible for anesthesia. PG and its metabolites in brain were resolved (HPLC) and quantitated following sacrifice at different behavioral endpoints. The results support the hypothesis that 5α-pregnan-3α-ol-20-one mediates the loss and the return of the righting response. The observed levels for PG were not consistent with such a role. Neither PG nor 5α-pregnan-3α-ol-20 produced analgesia.