Tryptophan, oxygenase, and sleep.

In summary, the, PGD2 and E2 are the major endogenous sleep-regulating substances, the former inducing physiological sleep and the latter, wakefulness, in rats, monkeys and probably in humans as well. Second, PGD synthase, the key enzyme in the regulation of sleep, is present mainly in the leptomeninges and choroid plexus, from which it is secreted into the CSF to become beta-trace protein. Third, PGD2 exerts its somnogenic activity at the ventro-rostral surface of the basal forebrain.