Brain peptide shapes learning and memory in the hippocampus

Cholecystokinin, abbreviated CCK, is familiar to most people as a hormone released after eating that regulates digestion. But CCK is also the most abundant neuropeptide in the central nervous system. What it does there has long been unclear. New research focuses on a specific group of neurons in the hippocampus, the brain region central to spatial memory and navigation.

What does CCK do in the hippocampus?

The hippocampus consists of multiple subregions, including CA1 and CA3. The study, published in eLife, shows that excitatory CCK neurons in the CA3 region form connections with CA1 neurons. When those connections are active, CCK is released. In mice, disabling the CA3-CCK-CA1 connection significantly impaired spatial learning and neuroplasticity (the ability of brain cells to strengthen or adjust connections). Reducing CCK gene expression in CA3 had similar effects.

Neuroplasticity is a core concept in memory research: it is the mechanism by which brain cells adjust their connections based on experience. If CCK helps regulate this process, that has broader implications for understanding memory problems in aging.

What does this mean for aging?

The study was conducted in adult mice and does not directly address humans or aging. Still, the finding is relevant: the hippocampus is one of the first brain regions affected in Alzheimer’s disease and in normal cognitive decline in later life. Better understanding which neuropeptides support hippocampal function is a step toward interventions that keep cognition healthy for longer. Whether CCK signaling declines with age is a question this research raises but does not answer.

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