Today, most experts acknowledge that environmental cues -- the people, places, sights and sounds an addict experiences leading up to drug use -- are among the primary triggers of relapses. It was an environmental cue (a ringing bell) that caused the dogs in Ivan Pavlov's famous experiments to salivate, even when they couldn't see or smell food.
Led by Hitoshi Morikawa, associate professor of neuroscience at The University of Texas at Austin, a team of researchers trained rats to associate either a black or white room with the use of a drug. Subsequently, when the addicted rats were offered the choice of going into either room, they nearly always chose the room they associated with their addiction.
Then one day, the researchers gave the addicted rats a high dose of an antihypertensive drug called isradipine before the rats made their choices. Although rats still preferred the room they associated with their addiction on that day, they no longer showed a preference for it on subsequent days. In fact, the lack of preference persisted in the isradipine-treated group in ways that couldn't be found in a control group -- suggesting the addiction memories were not just suppressed but had gone away entirely.
"The isradipine erased memories that led them to associate a certain room with cocaine or alcohol," said Morikawa.