Scientists Prevent Memory Problems from Sleep Loss with Signaling Molecule

When you're sleep deprived, you don't necessarily think fast on your feet. This isn't surprising. After all, sleep is a crucial period for memory consolidation. Now, though, scientists have discovered a particular region of the brain that's responsible for memory problems after sleep loss, and have found that by selectively increasing levels of a signaling molecule in these cells, they can prevent mice from having memory deficits.

In 2009, a group found that the cyclic AMP, or cAMP, signaling pathway played a role in sleep-loss-associated memory problems. Restoring levels of cAMP, though, prevented this effect.

"The challenge following this important study was to determine if the impact of sleep deprivation was mediated by particular regions of the brain and particular neural circuits," said Ted Abel, the senior author of the new study, in a news release. "We suspected that the hippocampus, the brain region that mediates spatial navigation and contextual memory, was critical."

In this case, the scientists engineered a non-pathogenic virus to harbor the gene encoding the receptor for the protein octopamine, which triggers cAMP pathway activation in fruit flies but isn't normally found in the brains of mice. Then, the researchers injected this virus into the hippocampus of mice so that the excitatory neurons in that region alone would express the octopamine receptor. They followed this up by giving the mice the ligand of the receptor, which is octopamine, which activated the receptors only where they were present.

So what did they find? The excitatory hippocampal neurons expressed the receptor. Not only that, but the scientists could selectively increase cAMP levels. They then sleep deprived some of these mice and gave them memory tests. In the end, they found that the sleep-deprived mice that received octopamine injections did not suffer the same memory problems as their sleep-deprived peers did.

While the findings only extend to mice, the scientists hope that for their next step, they can explore what cAMP is doing to help consolidate memory. In addition, they hope to eventually make their findings applicable to people.

"Thinking about people who do shift work or doctors who work long hours, if we can tackle the cognitive problems that result from sleep loss, that would be a great thing," said Robbert Havekes, one of the researchers.

The findings are published in the Journal of Neuroscience.