TUCSON, Ariz. – One in three Americans will suffer from chronic pain at some point in their lives, resulting in an estimated $635 billion per year in medical treatment and lost productivity. To better understand the multiple dimensions of pain, including sensory, emotional and cognitive aspects, Frank Porreca, PhD, and his research group in the Department of Pharmacology at the University of Arizona College of Medicine – Tucson have been awarded a $2.5 million, five-year R01 grant from the National Institute on Drug Abuse of the National Institutes of Health. David Borsook, MD, PhD, Professor of anesthesiology at Harvard Medical School, is a co-investigator on the 1 R01 DA 034975-01grant.
Chronic pain is defined as any pain lasting more than 12 weeks or pain that is longer than the expected time of healing. Whereas acute pain is a normal and essential mechanism that protects us from injuries, chronic pain is very different. Chronic pain persists after injuries have resolved, does not serve any useful purpose and is a burden to patients and society.
Dr. Porreca, UA professor of pharmacology and anesthesiology, and his laboratory study the neural circuits mediating pain in the brain and the spinal cord. In a key finding, the team has demonstrated that treatments that relieve the unpleasant feeling of pain also activate reward circuits and reinforce behaviors that result in the relief of pain.
“Pain is an emotion, both a sensation and a motivation. It is the unpleasantness of pain that produces strong motivation to get rid of it and to seek relief,” said Dr. Porreca.
“Pain can be thought of as analogous to other aversive states that produce motivation. For example, hunger is an aversive state, and when we are hungry we are motivated to seek relief and find food; when we are thirsty we are motivated to seek water; and when we are cold we are motivated to seek warmth. Relief of the aversive states, including pain, is rewarding. We are studying the reward circuits in the brain and their response to the relief of the aversiveness of pain,” Dr. Porreca explained.
Dr. Porreca’s team is evaluating the activation of brain reward circuits as a way to identify new treatments that effectively relieve pain so that new medications can be discovered. There are multiple competing emotions that create motivational drives, Dr. Porreca says, and “we have to investigate the brain mechanisms that underlie chronic pain in order to discover more effective medications.”
“Pain is a complex individual experience that depends on the context in which injuries may occur. We have to determine whether it is appropriate to respond to pain or to take other, more imperative action. For example, in a safe setting you respond to the pain and attend to the injury that may have caused it. However, in a situation where there is a threat to survival, responding to pain is less important.”
For example, stress can suppress pain so that escape and survival are possible, Dr. Porreca said. This commonly is seen in our daily lives, such as the lack of pain in individuals who may be injured in an automobile accident or the lack of pain an athlete may experience during competition. Dr. Porreca explained that the mechanism for pain probably has been activated in each instance, but the brain can modulate the process that produces the pain within the context of the injury.
Conversely, in chronic pain conditions, the brain may enhance or exaggerate the experience of pain and such conditions are very difficult to treat with conventional pain medications.
“Current medications used for chronic pain are ineffective for many people and have serious side-effects,” Dr. Porreca said. “The novel demonstration of pain relief as a reward provides an entirely new way to discover medicines for patients.”
Dr. Porreca collaborates with a multi-disciplinary team at the UA that includes Regents Professor Emeritus Victor Hruby, PhD, and Professor Robin Polt, PhD, both with the Department of Chemistry and Biochemistry.
Dr. Porreca works closely with Research Professor of Pharmacology Michael Ossipov, PhD, and Assistant Research Scientists Milena De Felice, PhD, Jennifer Xie, PhD, and Edita Navratilova, PhD, along with postdoctoral fellows, graduate students and visiting research fellows.
About Dr. Porreca
Frank Porreca, PhD, professor of pharmacology and anesthesiology at the UA College of Medicine – Tucson and a member of The University of Arizona Cancer Center, is widely regarded for his work as a principal investigator with the UA Pain Research Group, one of the world’s foremost pain research programs. Dr. Porreca’s current research focuses on the mechanisms of chronic pain states, including neuropathic, inflammatory, visceral, headache and cancer pain and mechanisms of opioid-induced hyperalgesia, a clinical phenomenon characterized by worsening pain, despite increasing doses of opioids.
He has served as editor-in-chief of Life Sciences, as editor of the Pharmacology Section for Pain and has authored more than 450 peer-reviewed papers. He is involved with numerous professional societies and is the founder and scientific organizer of the Spring Pain Research Conference, a biennial conference that attracts world-renowned members of pain laboratories in both academia and industry.
About the UA Pain Research Group
The Pain Research Group at the UA College of Medicine – Tucson studies the underlying causes of acute and chronic pain to promote the discovery of new targets for drug development with the ultimate goal of improved pain management. Current areas of investigation include cancer pain, skeletal pain, neuropathic pain, headache pain and inflammatory pain.
The group is a multi-disciplinary team consisting primarily of faculty from the UA Department of Pharmacology who collaborate with members of the UA Cancer Center; the UA Sarver Heart Center; the UA College of Medicine – Tucson Departments of Anesthesiology, Pathology and Neurology; the UA College of Science Departments of Molecular and Cellular Biology and Chemistry and Biochemistry, as well as with many extramural collaborators. The expertise of the group’s investigators encompasses a spectrum of molecular, neuroanatomical, neurochemical and neuropharmacological techniques.
About the UA Department of Pharmacology
One of five basic science departments at the UA College of Medicine – Tucson, the Department of Pharmacology conducts cutting-edge research on human diseases and their treatments. Areas of study include cancer, cardiovascular disease, immunopharmacology, toxicology, neurosciences and pain. Department faculty members seek to improve understanding of mechanisms of disease to promote the development of improved therapies and outcomes. The department educates medical and other health sciences students, physicians and scientists in all areas of pharmacology. For more information, please visit the website: www.pharmacology.arizona.edu