Dendritic spine formation in response to progesterone synthesized de novo in the developing Purkinje cell in rats.

The cerebellar Purkinje cell (PC) is a typical site for neurosteroid formation. We have demonstrated that this neuron possesses intranuclear receptor for progesterone and actively synthesizes progesterone de novo from cholesterol only during rat neonatal life, when the formation of the cerebellar cortex occurs dramatically. In this study, we therefore analyzed the effect of progesterone on dendritic spine formation of the PC. In vitro studies using cerebellar slice cultures from newborn rats showed that progesterone increases the density of PC dendritic spines in a dose-dependent manner. This effect was blocked by the progesterone receptor antagonist, RU486. Furthermore, trilostane, a specific inhibitor of progesterone synthesis, inhibited the increase of spine density. These results suggest that progesterone can promote dendritic spine formation, and endogenous progesterone synthesized de novo in the developing PC may induce such an effect.