Roles of Gastrin-Releasing Peptide Neurons in the Brain’s Clock for Light-Based Timing and Daily Rhythm Control

Chemogenetic stimulation of SCN gastrin-releasing peptide-producing neurons can induce phase shifts in behavioral rhythms.

• The suprachiasmatic nucleus (SCN) is the central circadian clock in mammals, regulating daily rhythms in behavior and physiology.
• SCN gastrin-releasing peptide-producing neurons (GRPNs) primarily project to the thalamus and hypothalamus.
• SCN GRPNs receive most of their synaptic inputs from within the SCN itself.
• Neither the absence of GRP nor the removal of SCN GRPNs significantly altered circadian locomotor activity rhythms or photic entrainment.
• Calcium imaging revealed that SCN GRPNs respond quickly to light stimulation, showing increased activity after exposure to white light.
• These findings indicate that while SCN GRPNs are involved in photic entrainment, their role may overlap with other neuronal populations.

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