A recent study from the University of Oxford suggests that histamine, the chemical infamous for causing allergy symptoms like hay fever, also plays a crucial role in boosting memory within the brain. Researchers found that a drug which increases histamine levels in the brain could improve memory accuracy by around 10 per cent.
Michael Colwell at the University of Oxford, who led the research, explained that histamine in the brain appears to influence 'novelty-linked arousal' – essentially, how alert individuals feel when encountering new information or stimuli. This understanding builds on existing knowledge that the brain contains receptors specifically for detecting histamine, particularly in areas vital for learning and memory. Previous animal studies have also supported the link between histamine and learning processes.
The team investigated the effects of elevated brain histamine by utilising pitolisant, a drug already approved for treating narcolepsy and Prader-Willi syndrome. Pitolisant works by binding to histamine 3 receptors, thereby increasing histamine levels throughout the brain. In a controlled experiment, 60 volunteers were divided into two groups, with one receiving pitolisant and the other a placebo. Brain scans conducted during memory tests revealed enhanced connectivity between histamine-producing regions and the hippocampus – a key memory processing area – in those administered pitolisant. This group subsequently demonstrated an 11 per cent improvement in retrieving learned information.
The findings could also shed light on some memory-related side effects associated with older antihistamine medications. Mr Colwell noted that many early antihistamines were able to cross into the brain, potentially impairing memory. He suggested this might explain why individuals taking these older drugs for extended periods sometimes reported difficulties with recall.
Despite the promising results, Mr Colwell strongly cautioned against attempting to use pitolisant as a 'smart drug' to enhance cognitive function in healthy individuals. He warned that such use would likely severely disrupt sleep, which could ultimately worsen memory in the long term. Dr Roland Seifert from Hannover Medical School in Germany echoed this sentiment, adding that the drug's restricted availability would make misuse challenging. Holger Stark from Heinrich Heine University in Düsseldorf, who helped develop pitolisant, highlighted that while the drug can restore impaired cognitive function and improve attention in patients with certain conditions, its effect is generally to normalise function rather than boost it beyond typical levels.
This research underscores the remarkable adaptability of the human body, demonstrating how a single molecule like histamine can be repurposed by evolution to serve vastly different functions – from triggering immune responses in the body to enhancing memory in the brain.