(Press-News.org) (Philadelphia, PA) - It's long been known that scratching evokes a rewarding and pleasurable sensation in patients with chronic itch. Now, researchers in the Department of Dermatology and Temple Itch Center at Temple University School of Medicine (TUSM) may be closer to understanding why.
Using advanced fMRI imaging, the researchers looked at activity in the brain while 10 chronic itch patients and 10 healthy subjects scratched an itch. They found that areas of the brain involved in motor control and reward processing were more activated in chronic itch patients while they scratched. This overactivity may help explain the addictive scratching experienced by these patients. The study findings were published June 15 by the Journal of Investigative Dermatology.
"Chronic itch is a major symptom in dermatological diseases such as atopic eczema and psoriasis and a bothersome symptom in other diseases like end-stage renal disease," says Hideki Mochizuki, PhD, Assistant Professor of Dermatology at TUSM, and first author of the study initiated by Gil Yosipovitch, MD, Chair of Dermatology at TUSM, and Director of the Temple Itch Center.
"Despite being pleasurable at first, ongoing scratching can lead to an increase in the intensity of itch as well as pain and permanent skin damage," Dr. Mochizuki continues. "That is why it is important to understand the cerebral activity that may be inducing this pathological scratching behavior."
In a previous study by Dr. Yosipovitch's group, researchers investigated the cerebral mechanisms of scratching and its association with pleasure in healthy volunteers only.
According to Dr. Yosipovitch, this new study is the first to investigate brain activity during scratching in chronic itch patients.
During the study, itch was induced by applying cowhage (a plant) to the right forearms of patients with chronic itch and study participants without chronic itch. The patients were then imaged using fMRI while they scratched the itch. Researchers found that brain activity spiked in the chronic itch patients in the supplementary motor area, premotor cortex, and primary motor cortex - areas that are associated with motor control and motivation to act. In addition, brain areas involved in reward circuit such as the striatum, cingulate cortex, caudate nucleus and orbitofrontal cortex were significantly more activated than in healthy subjects.
"Our findings may enable us to identify and advance the understanding of the brain network underlying the itch-scratch cycle in chronic itch patients," says Mochizuki. "This understanding could lead to new therapies for these patients."
Chronic itch affects millions of Americans and is defined as itching that lasts for more than six weeks. It may be located over the entire body, or it may be limited to a single area. The chances of developing chronic itch increase with age.
INFORMATION:
Coauthors are Hideki Mochizuki, Leigh Nattkemper and Andrew Lin from Temple, and Alexandru D.P. Papoiu, Robert Kraft, and Robert Coghill from Wake Forest University.
This study was funded by a grant from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (5ARO155904).
About Temple Health
Temple University Health System (TUHS) is a $1.8 billion academic health system dedicated to providing access to quality patient care and supporting excellence in medical education and research. The Health System consists of Temple University Hospital (TUH), ranked among the "Best Hospitals" in the region by U.S. News & World Report; TUH-Episcopal Campus; TUH-Northeastern Campus; Fox Chase Cancer Center, an NCI-designated comprehensive cancer center; Jeanes Hospital, a community-based hospital offering medical, surgical and emergency services; Temple Transport Team, a ground and air-ambulance company; and Temple Physicians, Inc., a network of community-based specialty and primary-care physician practices. TUHS is affiliated with Temple University School of Medicine.
Temple University School of Medicine (TUSM), established in 1901, is one of the nation's leading medical schools. Each year, the School of Medicine educates approximately 840 medical students and 140 graduate students. Based on its level of funding from the National Institutes of Health, Temple University School of Medicine is the second-highest ranked medical school in Philadelphia and the third-highest in the Commonwealth of Pennsylvania. According to U.S. News & World Report, TUSM is among the top 10 most applied-to medical schools in the nation.
Temple Health refers to the health, education and research activities carried out by the affiliates of Temple University Health System (TUHS) and by Temple University School of Medicine. TUHS neither provides nor controls the provision of health care. All health care is provided by its member organizations or independent health care providers affiliated with TUHS member organizations. Each TUHS member organization is owned and operated pursuant to its governing documents.
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