ENZYME SUSPECTED IN ADDICTION

An enzyme identified in the brains of animals fed continuous doses of
cocaine could be involved with the addiction process, according to
scientists at Rockefeller University in Manhattan. The finding could
ultimately lead to a better understanding of drug abuse and to the
development of new medicines to treat drug addiction.

James Bibb, working with Paul Greengard, a recent recipient of the Nobel
Prize in physiology or medicine, discovered the increased levels of the
enzyme, which is a brain protein called cyclin-dependent kinase 5, or Cdk5,
in animals repeatedly exposed to cocaine. Chronic cocaine exposure led to
changes in gene expression and the altered levels of Cdk5. This protein is
a kinase, or signaling molecule, that regulates the action of dopamine.
Dopamine, a neurotransmitter, is the key player in the brain's pleasure
pathway.

Blocking this signaling system, the Rockefeller scientists showed in a
recent study, had a major impact on the animal's behavior. The mice almost
doubled their activity level, suggesting that Cdk5's role in the brain
directly targets the dopamine system.

(snip)