Over a million people in the United States have Parkinson’s disease, a neurodegenerative disorder in which brain cells progressively die.
Sixty thousand people are diagnosed with the disease every year in the United States.
People with Parkinson’s disease have low concentrations of dopamine in their brain. Symptoms of the disease include tremor, extreme slowness of movement, rigidity, and impaired balance, as well as difficulties speaking and swallowing.
Parkinson’s disease was first identified approximately 200 years ago. However, there weren’t many treatments and therapies until the 1950s, when researchers first identified low dopamine levels in patients with Parkinson’s disease.
Since then, improving the function of the dopamine system through dopamine replacement therapy and other measures has been the standard treatment for people with Parkinson’s disease. Levodopa therapy is typically used to increase dopamine levels in nerve cells. As the disease progresses, however, it can start to lose effectiveness after 5-10 years of use.
Understanding “off time”
Patients with Parkinson’s disease may experience “off” episodes. These are periods of time when the patient’s medication stops working optimally and their symptoms come back before it’s time for their next scheduled dose of dopamine replacement therapy.
During an “off” episode, patients with Parkinson’s disease may have slow movement and rigidity, as well as difficulty doing things like getting out of bed without assistance, eating a meal without help, or walking out of an elevator without assistance. According to researchers, other symptoms could include tremor, a sense of weakness, and difficulty swallowing.
An “off” period could look different for each person with the disease. For example, some patients can have rapid onset of symptoms, while others experience a more gradual onset. “Off” periods can occur at different points of the day too, such as early morning muscle cramps, but “off” time can also occur throughout the day.
Not every person with Parkinson’s disease will experience “off” time. But a patient who does have “off” episodes should talk to their doctor about how to manage their condition. They should keep notes of how often, and when, “off” times occur and what symptoms they experience, so their doctor can have a good understanding of what’s happening.
New focus
Now there is another area of research: adenosine receptors.
Researchers have studied several receptors in the brain to gain insight into the disease. One sub-type that has particular interest is adenosine A2A receptors. As Parkinson’s disease advances, dopamine levels decrease and the number of adenosine A2A receptors increase, causing a patient’s motor function to further decline.
Since adenosine A2A receptors work with dopamine, it’s thought to play a role in impacting a patient’s motor function. Research suggests that adenosine A2A receptors help control activity of the dopamine system by acting like a brake on the activity of dopamine.
“Our current understanding is that dopamine facilitates movement and adenosine A2A receptors suppress it,” says neurological disorders researcher, Akihisa Mori, Ph.D., Fellow and Global Medical Lead CNS, of Medical Affairs for Kyowa Kirin Co., Ltd in Japan.
The future
This expanding area of research is exciting for Dr. Mori and those in the movement disorder community.
“This opens a new direction for our understanding of Parkinson’s disease,” says Dr. Mori, who’s been studying the adenosine receptor physiology since the 1990s.
Over the years, there’s been little innovation into understanding and controlling the disease beyond dopamine. But patients with Parkinson’s disease, caregivers, and doctors are eager to learn new ways to manage it.
“That’s why this new understanding of the role adenosine A2A receptors play with regards to dopamine holds so much promise,” says Dr. Mori.
For more information, patients can visit challengingparkinsons.com.