Motivation contributes to drug addiction: study

CHICAGO, Dec. 4 (Xinhua) -- The addictive behavior is fueled by motivation in the face of adverse consequences and constantly changing circumstances, researchers at the University of Michigan (UM) and the Open University in England found.

The findings have been newly published in the Journal of Neuroscience.

This concept differs from other studies in which rats and other animals repeat the same behavior, such as pressing a lever or poking their noses through a port, to get the drugs.

The researchers studied how male rats solved increasingly difficult puzzles to receive a cocaine reward. Since the puzzles always changed after weeks of testing, the rats' addiction-like behavior never became automatic or habitual.

The rats occupied chambers with puzzles, and they had to perform tasks that included spinning a wheel, pressing a lever and poking their nose into a hole. If they made mistakes in trying to solve a puzzle, the animals had to restart from the beginning.

Successfully completing a puzzle allowed the rats to self-administer small doses of cocaine. Over the course of the experiment, the rats continued solving the challenging puzzles, the study showed.

Brain regions that were important for regulating habits were not involved in drug-seeking. "Instead, other brain regions critical to motivation controlled drug-seeking in our rats," said Bryan Singer, the study's lead author and former UM psychology researcher who is now at the Open University.

"The rats' perseverance in drug-seeking, and increased rate of responding reflect the increasing motivation to obtain the drug," said Robinson, a UM professor of psychology and neuroscience. "And because they adjusted their behavior, it never became habitual."

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