Low Mood

Serotonin is a chemical in the brain that plays an important role in mood, sleep, and other functions. It works by attaching to different types of serotonin receptors on brain cells. These receptors act like "locks", with serotonin acting like a "key". Different types of serotonin receptors have different effects in the brain. Prucalopride is a licensed medication used to treat constipation. It acts on a particular serotonin receptor, called the serotonin 4 receptor. Researchers are interested in this receptor because understanding how it works in the brain may help us learn more about depression and could contribute to the development of new treatments in the future. The purpose of this study is to investigate the effects of prucalopride in people experiencing low mood. We will compare prucalopride with a placebo (a treatment with no active medication) to find out whether activating the serotonin 4 receptor affects sleep and aspects of thinking, including memory, attention and decision making.