Sleep Hormone May Hurt Memory
A recent study conducted by Gregg Roman of the University of Houston suggests that melatonin, the hormone that regulates sleep cycles in humans and animals, may contribute to memory loss. However, other researchers, including UC Irvine professor James McGaugh, believe that further research is needed to prove this claim.
Roman’s study used zebrafish, which were exposed to light in a tank of water. Zebrafish typically tend to swim away from light. However, when they swam away in this study, they were given a mild shock.
According NewScientist.com, Roman says that zebrafish have the potential to remember such conditions for days. As a result, after 20 minutes the zebrafish learned to swim closer to the light to avoid being shocked. Days later, the fish continued to swim closer to the light, demonstrating that they remembered the shock factor.
However, when melatonin was added to the equation, the zebrafish learned to swim close to the light but reverted to swimming away from the light after a short time.
‘This signifies that the fish had forgotten the shock,’ says Roman. This runs contrary to the current perceived effects of melatonin.
UCI professor Stephen Bondy defines melatonin as ‘a natural neurohormone, found in many tissues, that declines with age.’
Melatonin is found in the brain, more specifically in the pineal gland. Because of the brain’s tendency to produce less and less of the chemical over time, many scientist have drawn connections between the reduction of melatonin and the onset of memory-affecting diseases, such as Alzheimer’s.
In accordance with the traditional view on melatonin, McGaugh told NewScientist.com that the melatonin factor did not necessarily contribute to the memory loss. Instead, the zebrafish may have swum away from the light because of a biological mechanism triggered by melatonin. If this were proven, then the melatonin would be working outside of the zebrafish’s brain altogether, and the theory that melatonin has a negative effect on memory would be disproved.
More research is needed to show whether melatonin can negatively affect memory. However, even if Roman’s hypothesis is disproved, the benefits of melatonin for the treatment of memory-related diseases remains in question.
‘Melatonin is well known for its regulation of the sleep-wake cycle, but more work is needed on its anti-aging effect,’ Bondy said.
Still, melatonin is just one of the many signaling pathways in the brain. A signaling pathway is a series of actions that regulates a tendency or development in humans and animals, such as melatonin’s regulation of the sleep cycle.
Because many aspects of melatonin remain in question, the study of other signaling pathways may be important in reducing the effects of memory-related diseases. One researcher who is working with a newly-discovered signaling pathway is third-year department of pharmacology UCI graduate student Xiaobin Liu.
‘I am working on a relatively new signaling pathway, which might have [an] impact on memory. That signaling pathway is clear in helping maintain the awake state of animals, but we are [now] trying to figure out