"We hadn't predicted that we would find both positive and negative regulators from these peptides," Zhang said. "Why does the animal need this bidirectional regulation of learning? One possibility is that learning depends on context. There are certain things you want to learn for example, the worms in these experiments wanted to learn that they shouldn't eat this type of infectious bacteria. That's a positive regulation of the learning. But if they needed to eat, even if it is a bad food, to survive, they would need a way to suppress this type of learning."
Even more surprising for Zhang and her colleagues was evidence that the various insulin-like molecules could regulate each other.
"Many animals, including the humans, have multiple insulin-like molecules and it appears that these molecules can act like a network," she said. "Each of them may play a slightly different role in the nervous system, and they function together to coordinate the signaling related to learning and memory. By changing the way the molecules interact, the brain can fine tune learning in a host of different ways."
Going forward, Zhang said she hopes to characterize more of the insulin-like peptides as a way of better understanding how the various molecules interact, and how they act on the neural circuits for learning and memory.
Understanding how such pathways work could one day help in the development of treatment for a host of cognitive disorders, including dementia.
"The signaling pathways for insulin and insulin-like peptides are highly conserved in mammals, including the humans," Zhang said. "There is even some preliminary evidence that insulin treatment, in some cases, can improve cognitive function. That's one reason we believe that if we understand this mechanism, it will help us better understand how insulin pathways are working in the human brain."
|Contact: Peter Reuell|