Molecular mechanism of sleep regulation by prostaglandin D2.

Recent biochemical, molecular biological, and pharmacological experiments revealed that prostaglandin D synthase as well as prostaglandin D2 circulated in the ventricular system, subarachnoidal space, and extracellular space in the brain. Prostaglandin D2 then interacts with chemosensors or receptors on the ventro-medial surface of the rostral basal forebrain to initiate the signal to promote sleep. Prostaglandin D2 is, therefore, not a typical neurotransmitter but rather a 'neurohormone' or an 'informational substance' that circulates through the cerebrospinal fluid and transmits certain chemical messages to promote sleep. The mode of communication through the cerebrospinal fluid in the ventricular system and the extracellular space has advantages for global regulation of the brain to induce sleep.