The hunger-signaling gut hormone ghrelin can increase the number of nerve connections in a region of the brain crucial for the formation of new memories, reports a study in the March 2006 issue of Nature Neuroscience. This finding suggests unexpected ways that brain function may be influenced by what is going on elsewhere in the body.
Ghrelin is released by the empty stomach into the bloodstream, and can then activate receptors throughout the brain. In the hypothalamus, ghrelin acts to stimulate appetite, but its function in other brain regions is unknown. Tamas Horvath and colleagues now report that mice lacking the ghrelin gene have 25% fewer synapses in the hippocampus, which is known to be essential to learning. They find that injecting normal mice with extra ghrelin increases synapses in the hippocampus, and improves the animals' performance in several learning and memory tests.
These findings suggest that hunger may act through ghrelin to improve an animal's ability to learn and remember.
Tamas Horvath (Yale Medical School, New Haven, CT, USA)
Abstract available online.
(C) Nature Neuroscience press release.
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