Cognitive impairment within depression is common and appears to be at least partly separate from the mood component. It is not well targeted by current treatments and it may persist even after remission of mood symptoms. Therefore, it may be clinically beneficial to search for new therapies that are able to improve cognition in those who have, or are recovering from, depression.~Agonists of the serotonin receptor subtype 4 (5-HT4) have shown two profiles of effect in animal models: (i) a pro-cognitive profile, improving in learning and memory on a range of rodent paradigms; and (ii) an antidepressant-like profile, reducing depression and anxiety-related behaviours in rodent models of depression and anxiety.~A previous study in our group examining acute prucalopride administration (1mg) in 40 healthy human volunteers found improvements in learning and memory but little effect on emotional processing. This pro-cognitive effect was supported by a subsequent study where healthy volunteers received 7 days of prucalopride. In this study, prucalopride led to both better performance on a visual memory task, and increased activation in the hippocampus and an associated memory processing region in response to a memory stimulus. As short-term treatment with clinically-effective antidepressants such as SSRIs is known to produce positive biases in the processing of emotional information in healthy volunteers, this lack of effect on emotional processing was not consistent with prucalopride having antidepressant potential, and is surprising considering the strength of the animal data. One factor that has not yet been explored is whether the translation was limited due to the low dose of prucalopride used in our previous study.~Therefore, we wish to see if we (i) can translate this pro-cognitive effect of prucalopride into participants with a previous history of depression and current mild cognitive issues; and (ii) can use a full treatment dose of prucalopride to evaluate its effect on emotional processing.
The current study has two aims:~To test the effect of 5-HT4 receptor agonism on cognition (including memory, attention and cognitive control) in individuals with previous history of depression.~To explore if prucalopride has an effect on emotional processing biases consistent with its effects on serotonin.