Catching a good night’s sleep can make you feel like a million bucks. But for some of us, the quality of sleep we manage to get is always compromised by a sleep disorder. A recent study by U of T researchers has discovered a link between human REM sleep behaviour disorder (RBD) and neurodegenerative diseases like Parkinson’s. Those who suffer from RBD experience a loss of muscle powerlessness, and inevitably begin to act out their dreams.
In an interview with The Varsity, Dr. John Peever, lead author of the study, explained how dream enactment caused by RBD can be dangerous for both the dreamer and their bed partner. “In the middle of the night, the person will throw themselves through their closet door or break their wife’s neck. It often results in the wife tying her husband to their bed in order to protect herself,” Peever explains.
The cause of RBD is unknown; evidence shows the disorder may be due to reduced brain inhibition of particular neurotransmitters. The main goal of the current study was to see whether mice with deficient glycine and GABA transmissions exhibited REM motor behaviours. Glycine and GABA transmissions act as inhibitory neurotransmitters during REM sleep, helping to keep muscle atonia, which is the loss of muscle strength.
When asked about brain inhibition works in mice, Peever replied that “we know symptoms, we know what happens, but we don’t know what part of the brain has gone wrong. We need to look to see if the inhibitor part of the brain is degenerating.”
In order to study brain inhibition in mice, the mice were genetically altered so that they exhibited 70 per cent glycine reduction and 91 per cent reduction in GABA receptor inhibition. This combination mirrors the mutation common to human receptors in RBD patients. The mice were also given melatonin and clonazepam, drugs commonly used to treat human RBD.
When the mice consumed the drugs, researchers found that brain inhibition was strengthened for the duration of the drug intake. However, once treatment was terminated, RBD symptoms came back. Peever explains that “it’s like when you’re on Advil for a headache. The Advil helps relieve the pain but has not helped to cure it. The symptoms can keep coming back.”
These findings leave the door open to finding a cure for RBD and making advancements in drug treatments. Advancement in RBD treatment is an important goal because, as revealed by the study, 60 to 80 per cent of RBD patients also suffer from Parkinson’s disease. When asked about the significance of RBD treatments, Peever replied, “If we treat RBD we could have direct implications for the discovery of the treatment of Parkinson’s disease.”
Finding underlying triggers for RBD could help save lives and prevent further advancement of diseases. Although Parkinson’s is just one disorder linked to RBD, the sleep disorder is associated with stroke and brain lesions. The current study provides evidence that impaired inhibitory transmission triggers are a potential mechanism for RBD. Peever noted that “there could be many causes and triggers for RBD. …[I]t is important to understand that RBD may not cause Parkinson’s, but provides us with a link. Both disorders could be caused by the same thing which is why they are associated together.
“The bottom line is we need to develop a drug that will cure these diseases instead of just helping the symptoms. If we can discover more links then we will begin to understand more about both disorders,” says Peever.
