Adult rabbit brain synthesizes retinoic acid

Tissues of adult rabbit brain were shown to enzymatically oxidize retinol and retinaldehyde to retinoic acid, a potent stimulator of gene expression. Rates of retinoic acid synthesis by the cerebrum, cerebellum, and meninges were comparable to, or exceeded, rates measured with rat liver, an organ known to have a relatively high capacity to synthesize retinoic acid. These results, taken together with previous observations that the adult brain contains retinoic acid-activated transcription factors and cellular retinoid-binding proteins, suggest that retinoids may play an important role in the adult central nervous system.