|
In the forefront of pain research are scientists supported by the National Institutes
of Health (NIH), including the NINDS. Other institutes at NIH that support pain
research include the National Institute of Dental and Craniofacial Research,
the National Cancer Institute, the National Institute of Nursing Research, the
National Institute on Drug Abuse, and the National Institute of Mental Health.
Developing better pain treatments is the primary goal of all pain research being
conducted by these institutes.
Some pain medications dull the patient's perception of pain. Morphine is one
such drug. It works through the body's natural pain-killing machinery, preventing
pain messages from reaching the brain. Scientists are working toward the development
of a morphine-like drug that will have the pain-deadening qualities of morphine
but without the drug's negative side effects, such as sedation and the potential
for addiction. Patients receiving morphine also face the problem of morphine
tolerance, meaning that over time they require higher doses of the drug to achieve
the same pain relief. Studies have identified factors that contribute to the
development of tolerance; continued progress in this line of research should
eventually allow patients to take lower doses of morphine.
One objective of investigators working to develop the future generation of
pain medications is to take full advantage of the body's pain "switching center"
by formulating compounds that will prevent pain signals from being amplified
or stop them altogether. Blocking or interrupting pain signals, especially when
there is no injury or trauma to tissue, is an important goal in the development
of pain medications. An increased understanding of the basic mechanisms of pain
will have profound implications for the development of future medicines. The
following areas of research are bringing us closer to an ideal pain drug.
Systems and Imaging: The idea of mapping cognitive functions to precise
areas of the brain dates back to phrenology, the now archaic practice of studying
bumps on the head. Positron emission tomography (PET), functional magnetic resonance
imaging (fMRI), and other imaging technologies offer a vivid picture of what
is happening in the brain as it processes pain. Using imaging, investigators
can now see that pain activates at least three or four key areas of the brain's
cortex-the layer of tissue that covers the brain. Interestingly, when patients
undergo hypnosis so that the unpleasantness of a painful stimulus is not experienced,
activity in some, but not all, brain areas is reduced. This emphasizes that
the experience of pain involves a strong emotional component as well as the
sensory experience, namely the intensity of the stimulus.
Channels: The frontier in the search for new drug targets is represented
by channels. Channels are gate-like passages found along the membranes of cells
that allow electrically charged chemical particles called ions to pass into
the cells. Ion channels are important for transmitting signals through the nerve's
membrane. The possibility now exists for developing new classes of drugs, including
pain cocktails that would act at the site of channel activity.
Trophic Factors: A class of "rescuer" or "restorer" drugs may emerge
from our growing knowledge of trophic factors, natural chemical substances found
in the human body that affect the survival and function of cells. Trophic factors
also promote cell death, but little is known about how something beneficial
can become harmful. Investigators have observed that an over-accumulation of
certain trophic factors in the nerve cells of animals results in heightened
pain sensitivity, and that some receptors found on cells respond to trophic
factors and interact with each other. These receptors may provide targets for
new pain therapies.
Molecular Genetics: Certain genetic mutations can change pain sensitivity
and behavioral responses to pain. People born genetically insensate to pain-that
is, individuals who cannot feel pain-have a mutation in part of a gene that
plays a role in cell survival. Using "knockout" animal models-animals genetically
engineered to lack a certain gene-scientists are able to visualize how mutations
in genes cause animals to become anxious, make noise, rear, freeze, or become
hypervigilant. These genetic mutations cause a disruption or alteration in the
processing of pain information as it leaves the spinal cord and travels to the
brain. Knockout animals can be used to complement efforts aimed at developing
new drugs.
Plasticity: Following injury, the nervous system undergoes a tremendous
reorganization. This phenomenon is known as plasticity. For example, the spinal
cord is "rewired" following trauma as nerve cell axons make new contacts, a
phenomenon known as "sprouting." This in turn disrupts the cells' supply of
trophic factors. Scientists can now identify and study the changes that occur
during the processing of pain. For example, using a technique called polymerase
chain reaction, abbreviated PCR, scientists can study the genes that are induced
by injury and persistent pain. There is evidence that the proteins that are
ultimately synthesized by these genes may be targets for new therapies. The
dramatic changes that occur with injury and persistent pain underscore that
chronic pain should be considered a disease of the nervous system, not just
prolonged acute pain or a symptom of an injury. Thus, scientists hope that therapies
directed at preventing the long-term changes that occur in the nervous system
will prevent the development of chronic pain conditions.
Neurotransmitters: Just as mutations in genes may affect behavior, they
may also affect a number of neurotransmitters involved in the control of pain.
Using sophisticated imaging technologies, investigators can now visualize what
is happening chemically in the spinal cord. From this work, new therapies may
emerge, therapies that can help reduce or obliterate severe or chronic pain.
Hope for the Future
Thousands of years ago, ancient peoples attributed pain to spirits and treated
it with mysticism and incantations. Over the centuries, science has provided
us with a remarkable ability to understand and control pain with medications,
surgery, and other treatments. Today, scientists understand a great deal about
the causes and mechanisms of pain, and research has produced dramatic improvements
in the diagnosis and treatment of a number of painful disorders. For people
who fight every day against the limitations imposed by pain, the work of NINDS-supported
scientists holds the promise of an even greater understanding of pain in the
coming years. Their research offers a powerful weapon in the battle to prolong
and improve the lives of people with pain: hope.
Prepared by: Office of Communications and Public Liaison
National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD
Continue this article...
|
