For many this is about 10 times the caffeine as soda - a common beverage mixed with alcohol.
With repeated exposure to the cocktail, the mice became more active and researchers detected increased levels of a protein that marks long term changes in neurochemistry.
Teenagers who mix energy drinks with alcohol react as if they were on cocaine, new research claims.
Results from the study showed that adolescent mice given high-caffeine energy drinks mixed with alcohol showed physical and neurochemical signs similar to mice given cocaine, Purdue University reported.
"That's one reason why it's so hard for drug users to quit because of these lasting changes in the brain", authors explained in a statement.
Consequences from drinking caffeinated alcoholic beverages last into adulthood as an altered ability to deal with rewarding substances, the study said. The team exposed them to caffeinated alcohol during adolescence and wanted to see if these mice would later consume higher amounts of an artificial sweetener called saccharine.
While this sounds positive, it suggests such a mouse would use more cocaine to get the same feeling as a control animal.
"It seems the two substances together push them over a limit that causes changes in their behaviour and changes the neurochemistry in their brains", said assistant professor van Rijn. "They may then use more cocaine to get the same effect", the researcher said. They predicted that if the mice exhibited a numbed sense of reward, they would consume more saccharine.
It is illegal to carry out such a study in humans, but changes seen in mouse brains with drugs of abuse have been shown to correlate to be similar.
The age of the mice in the study indicates adolescent brains may be particularly sensitive to the effects of mixing alcohol and caffeine, as is true with many drugs. Their next project will test ethylphenidate, a drug similar to methylphenidate used to treat attention deficit hyperactivity disorder, or ADHD.