For the first time ever, scientists at the UCLA have measured the release of the peptides hypocretin and melanin concentrating hormone (MCH) within humans. Hypocretin’s release is increased when the person is happy, but minimal when they are upset. MCH levels are maximized when the subject is asleep, but those levels diminished awake.
“The current findings explain the sleepiness of narcolepsy, as well as the depression that frequently accompanies this disorder” explains Jerome Siegel, professor of psychiatry and director of the Center for Sleep Research at UCLA. The measurable changes of these peptides’ release will eventually allow researchers to develop medications that target the changes in brain chemistry.
In 2000, Siegel was the first to show a biological cause of narcolepsy when he found that people who suffer from the illness had 95 percent less hypocretin nerve cells for in their brain than people who don’t have narcolepsy. Due to the strong affiliation between depression and narcolepsy, Siegel expanded his study by researching how hypocretin could be connected to depression.
Image Source: micah.sparacio.org
Siegel retrieved information on hypocretin and MCH levels from the patients who had intracranial depth electrodes implanted in their brains. The patient’s actions were recorded while they ate, fell asleep, woke up, were social with other patients, and watched television. Every 15 minutes, the patients’ activity was recorded along with the release levels of the peptides. Each waking hour, the patient filled out a questionnaire where they rated with mood and attitudes.
Siegel found that positive emotions, social interactions, and the act of waking up had higher hypocretin levels, while the levels of MCH were at their highest when the patient was falling asleep and were at their lowest when the patient wasn’t being social. “These results suggest a previously unappreciated emotional specificity in the activation of arousal and sleep in humans” Siegel explained. “The findings suggest that abnormalities in the pattern of activation of these systems may contribute to a number of psychiatric disorders”
Siegel mentioned that several drug companies are in the process of developing hypocretin antagonists to be used as sleeping pills, but this study means that not only will these drugs induce sleep, but they will also influence the person’s mood.
Recent studies have suggested that depression-fighting drugs, like selective serotonin reuptake inhibitors (SSRIs) may have the same effect as a placebo as they are not based on the changes in neurotransmitter levels. Because as many as 10% of the US population suffers from depression, I think this study is a breakthrough in our knowledge on depression and I hope that this will lead to the production of a drug that can balance the release of these neurotransmitters.
Kathleen Leask
