Gut hormone ghrelin (bottom) increases synapse density (arrowheads) and improves memory.
HORVATH/MACMILLAN
The growling stomach produces the hormone ghrelin, which stimulates fat storage and appetite by binding neurons in the hypothalamus. But ghrelin also binds neurons in the hippocampus—a center for forming memories.
Horvath's team shows that ghrelin's hippocampal action promotes long-term potentiation and a higher synaptic density in the CA1 region of the hippocampus. Both characteristics correlated with improved spatial memory and learning.
The authors injected rodents with ghrelin and used three behavioral tests that rely on hippocampal memory functions—exploring different arms of a plus-shaped maze and two foot-shock avoidance tests. In each, ghrelin improved memory performance in a dose-dependent manner. Performance was improved 20–30%...
