Researchers at the University of Colorado at Boulder are exploring chemical links between the brain and body that could lead to progress against a host of poorly understood diseases such as multiple sclerosis, muscular dystrophy and AIDS.
For five years, psychology Professors Steven Maier and Linda Watkins have lead a team of 35 researchers studying communication pathways between the brain and the immune system. Maier will describe the group's latest findings in a plenary lecture June 14 at the Fifth National Conference on Drug Abuse, Immunomodulation and AIDS in Nashville, Tenn.
Research at CU-Boulder and elsewhere has shown that the brain and the immune system work to regulate each other, Maier said. But as recently as 15 years ago, the immune system was thought to function autonomously.
Knowing how the body's systems work and interact is an essential step in allowing chemists and biologists to create "designer drugs" to intervene against specific diseases, Maier said. The research also offers promise in fighting chronic pain and mental disorders such as depression, anxiety and schizophrenia.
"Until all these pathways are understood you can't understand these disorders and how we might intervene," Maier said. "The body is extremely complex, which is why we still have diseases we cannot cure."
Maier and Watkins' research looks at four main areas: the impact of stress on the immune system; how the immune system communicates with the brain; the role of the immune system in regulating pain; and the role brain chemistry plays in mediating stress. All the research studies are done with rats, which have central nervous systems that are similar to human systems.
While the brain was long thought to control the human immune system, Maier, Watkins and others documented that the immune system also sends signals back to the brain through the peripheral nervous system. This two-way chemical communication allows the brain to gather information about an infection and organize against diseases.
Their finding of the key relay in this communication between the immune system and the brain, the vagus nerve, also answered the question of how the brain knows the body is infected.
A common example of the brain's response to an infection is fever, Maier said. Fever both raises the body's temperature to a point where bacteria can't grow as well and it also causes immune cells to replicate more quickly.
"It's a double whammy," he said. "The last thing you want to do when sick is drive down a fever." Like many processes, however, fever also can go beyond the point of helpfulness to become harmful.
In a similar way, Maier said he believes that depressed mood is a useful function to some extent because it causes people to feel lethargic and to avoid exertion and to rest. Lack of motion is helpful is assisting recuperation from injuries and infections.
"We believe you want to rest so that the energy can go to feed the fever," he said.
But depression also can go beyond beneficial levels to become a problem, leading Maier to note that what may have been adaptive in the human species 10,000 years ago may be maladaptive today because our environment is changing faster than our genes. Evidence exists that depression has increased over the last 40 years, he said.
Another area in which knowledge of the body's communications systems could be helpful is the alleviation of chronic pain. "We have good reason to believe that chronic pain may be maintained by the immune system that is sending these signals," he said.
Maier's talk was titled "Bi-directional Immune/Brain Communication." His research work is funded by the National Institutes of Health and private companies.