Study in The Journal of Neuroscience shows that elevated levels of enkephalins in mice were associated with decreasing ability in behavioral tests.
Researchers from the Gladstone Institute of Neurological Disease determined in mouse models that modulating the activity of enkephalin peptides in the brain might reduce the cognitive deficits seen in Alzheimer’s disease (AD). Enkephalins are part of the endogenous opioid system, which modulates learning, memory, and other brain functions.
The team examined enkephalin functions in a transgenic mouse model of AD. They found increased levels of preproenkephalin mRNA and enkephalin in brain regions important for memory that are affected in early stages of AD.
When the scientists genetically manipulated the mice to make them more or less susceptible to neuronal damage, they discovered that the enkephalin levels were also affected. Furthermore, as levels of the enkephalins increased, the ability of mice to complete behavioral tests declined.
Compounds that blocked opioid receptors through which enkaphalins exert their effects reduced cognitive deficits. The investigators also showed that AD patients had increased levels of enkephalins in brain regions affected by the disease.
The study is published May 7 in The Journal of Neuroscience.