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Tetrodotoxin administration in the suprachiasmatic nucleus prevents NMDA‐induced reductions in pineal melatonin without influencing Per1 and Per2 mRNA levels
Blocking nerve signals in the brain's body clock stops NMDA from lowering night-time melatonin without changing clock gene activity
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Abstract
Sodium-dependent action potentials in the suprachiasmatic nucleus are necessary for light to suppress melatonin levels but not for increasing circadian clock gene mRNA levels.
- Light exposure during the night increases mRNA levels of the circadian clock genes Per1 and Per2 in the suprachiasmatic nucleus.
- Light exposure also suppresses melatonin levels in the pineal gland.
- Tetrodotoxin (TTX) inhibits the ability of light to increase Per1 and Per2 mRNA levels and to suppress pineal melatonin levels.
- N-methyl-D-aspartate (NMDA) can still increase Per1 and Per2 mRNA levels even when TTX is present, indicating that action potentials are not required for this response.
- However, NMDA's ability to suppress pineal melatonin levels is inhibited by TTX, suggesting a separate mechanism for this action.
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