Daily gene activity in the pituitary depends on increased sensitivity caused by the hormone melatonin

The elimination of melatonin leads to suppressed expression of the clock gene Period1 and increased release of pituitary prolactin in rodent cells.

• The expression of the clock gene Period1 in rodent pituitary cells is influenced by the activation of melatonin receptors.
• Melatonin activates the adenosine A2b receptor, which is important for the rhythmic expression of Period1.
• Removing melatonin disrupts the normal cycling of Period1 expression.
• Increased prolactin release occurs when melatonin's effects are eliminated, highlighting a link between circadian signals and hormone release.
• These findings suggest an interaction between melatonin and adenosine signaling that contributes to circadian rhythms in gene expression.

Simplified