Midazolam, a drug used in people with anxiety disorders, makes rats less empathetic, according to a study by scientists at the University of Chicago, reported in the journal Frontiers in Psychology.
During the experiments, rats that had previously received midazolam decided to release other rats trapped in a cage much less frequently than the control group.
Earlier research has confirmed that rats have an intrinsic motivation to help other rodents in trouble, and learn quickly to open their cages to free their mates. However, after the administration of midazolam, the fate of the imprisoned colleagues became indifferent to them. The only motivation to open the cage was the sweet snack placed in it, suggesting that helping the trapped rats is conditioned by an emotional response, which in turn is inhibited by the psychotropic drug.
The researchers also compared the rats’ corticosterone levels when they first met another caged rat. Rodents with low or moderate levels of the stress hormone most frequently attempted to release their mates. The rats with the highest corticosterone levels were the least likely to help.
The author of the study, Dr. Peggy Mason, notes that high levels of stress are more paralyzing than motivating for rodents, as it is for humans.