Serotonergic pre-treatments block in vitro serotonergic phase shifts of the mouse suprachiasmatic nucleus circadian clock

Low concentrations of serotonin-related compounds completely blocked phase-shifts induced by serotonin treatment in isolated mouse SCN.

• The suprachiasmatic nucleus (SCN) exhibits a circadian clock that operates with distinct properties when isolated in vitro.
• Previous findings indicate that serotonergic stimuli can phase-shift the SCN clock in vitro, but results vary in vivo.
• In vitro treatment with serotonin or its agonists led to complete inhibition of subsequent phase-shifts when pre-treated with specific serotonin-related compounds.
• L-tryptophan treatment may induce internalization of serotonin receptors, affecting their availability for signaling.
• The density of serotonin receptors on SCN clock neurons may be altered by prior serotonin signaling, influencing the clock's sensitivity to phase modulation.

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