Rat Studies Cut Dopamine by 99%, Leaving Sugar Pleasure Intact but Motivation Collapsed
Updated
Updated · spacedaily.com · Aug 23
Rat Studies Cut Dopamine by 99%, Leaving Sugar Pleasure Intact but Motivation Collapsed
2 articles · Updated · spacedaily.com · Aug 23
Summary
University of Michigan researchers found rats with up to 99% of dopamine destroyed still showed normal “liking” facial reactions to sugar, even as their drive to seek food largely vanished.
University of Washington mice engineered to make no dopamine still preferred sucrose and saccharin over water, but initiated fewer drinking bouts and would starve beside food without daily L-dopa.
A separate high-dopamine mouse model—with only 10% of the normal dopamine transporter and about 70% more synaptic dopamine—reached sweet rewards faster, while liking reactions stayed unchanged.
Haloperidol experiments and lever-versus-chow tests similarly showed dopamine blockade cuts willingness to work for food rather than appetite itself, supporting a split between motivation and pleasure circuits.
The work has helped recast addiction as craving that can outlast enjoyment, though some researchers still argue dopamine mainly signals prediction errors or movement vigor rather than reward.