April 12, 2006 -- When stress strikes, a certain hormone may boost binge behavior, researchers report in BMC Biology.
The findings may help explain why stress sometimes leads to binge eating, drug addiction relapse, "and other excessive pursuits of rewards," write University of Michigan psychology researcher Susana Pecina, PhD, and colleagues.
Pecina's team studied rats, not people. But the stress hormone the researchers focused on -- called corticotropin-releasing factor (CRF) -- is found in people, too.
CRF may affect a brain area called the nucleus accumbens to nudge rats -- and maybe people -- to go all out to seek rewards, according to Pecina's study. If so, stress may set the stage for binge behavior.
Trained to Crave Sugar
First, the researchers trained young male rats to press one of two levers to get a single pellet of sugar. The rats later learned that they could get three sugar pellets if they pressed that lever when they heard a 30-second tone.
Next, the researchers injected either salt water, high or low CRF doses, or amphetamines into the rats' nucleus accumbens, with a two-day break between injections.
Amphetamines have been shown to increase reward-seeking behavior in rats, while salt water shouldn't have any effect on binge behavior, the researchers note.
Bringing on the Binge
The researchers checked how often each rat pressed the lever linked to the sugar pellets after each type of injection.
After getting amphetamines or the high CRF dose, the rats pressed the lever more often for a minute or so. Amphetamines and the high CRF dose had the same effect.
The rats seemed to seek rewards -- the sugar pellets -- more than usual under CRF's influence, the researchers write.
Pecina's team adds that the rats weren't in a stressful situation, and that the short spike in lever-pressing looked like a short sugar binge, not an attempt to soothe negative brain effects with CRF.