The Biology of . . . Addiction

The rats in Stanley Glick's lab are junkies. They spend their days and nights lounging around in steel cages, twiddling their claws, waiting for the next hit. Each rat has a small plastic tube protruding from the base of its skull. Once a day, for an hour, each tube is connected to an infusion pump that controls a syringe containing a common addictive substance: morphine, cocaine, nicotine, or methamphetamine. The rats are trained to pull levers for water, but for one hour each day they can use the same system to mainline as much of the drugs as they want. And they want. "Just about any drug that humans abuse, animals will self-administer," Glick says.