Choroid plexus is an additional source of melatonin in the brain

Area of Science:

• Neuroscience
• Endocrinology
• Cell Biology

Background:

• Melatonin, a hormone regulating circadian rhythms, is found in cerebrospinal fluid (CSF).
• The exact brain regions responsible for de novo melatonin synthesis, beyond the pineal gland, remain largely unidentified.
• The choroid plexus (CP) is a potential extrapineal source of central nervous system (CNS) melatonin.

Purpose of the Study:

• To investigate whether the choroid plexus (CP) synthesizes melatonin within the brain.
• To identify the enzymes involved in melatonin synthesis in the CP.
• To determine if melatonin synthesis in the CP exhibits circadian regulation.

Main Methods:

• Analysis of the four key enzymes required for melatonin synthesis in rat CP tissue.
• Assessment of arylalkylamine N-acetyltransferase (AA-NAT) expression and localization in rat CP.
• Melatonin synthesis detection in porcine CP explants.

Main Results:

• The four essential enzymes for melatonin synthesis were confirmed in rat CP.
• Arylalkylamine N-acetyltransferase (AA-NAT) demonstrated circadian expression in both male and female rat CP, localizing to mitochondria within epithelial cells.
• Porcine CP explants successfully synthesized melatonin, though not in a circadian manner.

Conclusions:

• The choroid plexus (CP) serves as a local source of melatonin within the central nervous system (CNS).
• CP-derived melatonin likely contributes to the overall melatonin concentration in the cerebrospinal fluid (CSF).
• Melatonin synthesis in the CP may be influenced by both internal clock mechanisms and external hormonal signals.