Polarised light micrograph of crystals of the chemical histamine
ALFRED PASIEKA/SCIENCE PHOTO LIBRARY
Histamine primarily drives immune responses throughout the body, a fact well known to those suffering from hay fever. However, in the brain it performs a distinct function; a recent study showed that increasing histamine levels can boost memory accuracy by roughly 10%.
Michael Colwell of the University of Oxford explained, “We believe this reflects changes in novelty‑linked arousal – the level of alertness triggered by new stimuli in the environment.”
Histamine receptors have long been identified in the brain, and they are densely clustered in regions associated with learning and memory, according to Colwell. Animal research further supports histamine’s involvement in learning processes.
Such effects could account for the memory impairments observed with older antihistamine medications that penetrate the brain. As Colwell notes, these drugs can impair recall when taken chronically.
What occurs when brain histamine levels rise? Historically, this was difficult to test in humans, but Colwell and his team recognized that pitolisant—an approved narcolepsy medication—effectively raises histamine by binding to histamine‑3 receptors throughout the brain.
To evaluate this, the researchers enrolled 60 participants, administering pitolisant to half and a placebo to the other half. Brain imaging via MRI revealed increased connectivity between histamine‑producing regions and the hippocampus in the pitolisant group, and these participants performed 11% better on memory tasks conducted during scanning.
Colwell cautioned that pitolisant should not be considered a cognitive enhancer; its sedative effects could disrupt sleep, ultimately impairing memory over time.
Roland Seifert of Hannover Medical School in Germany notes that pitolisant is unlikely to be misused as a smart drug, given its limited availability. He also emphasized that the study validates the translation of animal findings to humans and suggests that targeting histamine receptors could become a therapeutic approach for various brain disorders.
Individuals using pitolisant for narcolepsy or Prader‑Willi syndrome have reported heightened attention and alertness, according to Holger Stark of Heinrich Heine University, a co‑creator of the drug. He observes that the medication typically restores impaired cognition and attention rather than pushing performance beyond typical levels.
Histamine’s dual roles illustrate how evolution repurposes molecules for diverse physiological needs. As Colwell remarks, this underscores the body’s economical use of existing pathways.
