From the June 30 issue of Science News:

At Brookhaven National Laboratory in Upton, N.Y., researchers injected healthy volunteers with radioactively labeled cocaine at doses far too small to induce addiction or a "high." They discovered that the drug binds strongly to human heart cells, particularly in the left ventricle. Study leader Nora D. Volkow says the research, undertaken with permission from the Food and Drug Administration, suggests that cocaine overdose may pose a triple threat to the heart.

Scientists already knew that cocaine abuse can cause heart failure through its indirect effects -- constricting blood vessels and manipulating the brain to disrupt normal heart rhythm. But in binding directly to cardiac tissue, cocaine may add a third lethal punch by slowing the passage of sodium ions into heart cells and/or stimulating the release of the neurotransmitter norepinephrine, which can lead to irregular heartbeat, or arrhythmia, Volkow asserts.

She and her colleagues also found that large concentrations of cocaine bind to the aorta, the major artery carrying blood from the heart. This, they say, may account for some of the blood vessel damage associated with cocaine overdose.

In a separate study ... Volkow's team and collaborators at the State University of New York at Stony Brook examined human brain scans highlighting nerve-cell receptors for the neurotransmitter dopamine. ... Addicts who had been off the drug for one week or less showed about 30 percent fewer dopamine receptors than ... healthy volunteers. Those who had abstained for a full month had about the same number of receptors as the healthy controls.