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Drug addiction relapse neurons identified

Jasbird Jasbird#dead-mail-box# at myrealbox.com
Thu Aug 21 02:14:22 EST 2003


Drug addiction relapse neurons identified

21 August 2003, LONDON, By Claire Bennett

US researchers have linked the behaviour of seeking drugs after a
period of abstinence to specific nerve cells in a part of the brain
called the nucleus accumbens.

Previous studies have shown that drug addiction depends on the
mesocorticolimbic dopamine system innervating the nucleus accumbens.

Dr Udi Ghitza and colleagues from Rutgers University tested whether
the accumbens neurons exhibit responses to external stimuli previously
associated with self-administration of cocaine by rats.

The rats learnt that on hearing a tone they could press a lever and
self-administer cocaine. No cocaine was available if the animal
pressed the lever in the absence of the tone.

Microelectrodes were attached to the brains of the animals and these
recorded the activity of single neurons in the nucleus accumbens.

After two weeks of self-administration of cocaine, the lever was
removed and no tone sounds were made. The animals abstained from the
drug for almost a month.

When the lever was returned to the cage, the animals ignored it when
no cocaine and no tone were provided. However, when the original tone
was made, the animals began to press the lever at a high rate even
though no cocaine was available.

During this relapse into drug seeking, the neurons - in an area of
nucleus accumbens known at the shell - were activated by the tone.

The rats eventually stopped pressing the lever when the tone was made.
However, nucleus accumbens neurons still responded to the tone.

Dr Mark West, one of the co-authors, says, " This activity may reflect
the processing of memories that persist even after a long abstinence
and may partially explain why environmental cues can provoke a

And he adds, "This suggests that the existence of a neuroadaptation
that may make individuals more vulnerable to assuming drug-taking

Reference: Ghitza et al, Journal of Neuroscience 2003;23:7239-7245

© HMG Worldwide 2003

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