The sex drug Viagra appears to cut the effects of stress on the heart by 50 percent, according to a report by researchers at Johns Hopkins University.The report shows that the drug, which is normally used to treat impotence, blunts the strengthened heartbeat caused by chemically induced stress.

Earlier research by Dr. David Kass, lead author of the study, found that Viagra blocked the short-term effects of hormonal stress in the hearts of mice and also prevented the long-term cardiac effects of chronic high blood pressure in mice.

In the current study, 35 healthy men and women with no signs of heart disease received two separate injections of dobutamine over three hours. Dobutamine increases heart rate and pumping strength.

Between injections, the patients were given Viagra or a placebo. Then they all were given a second dobutamine injection. After the first injection of dobutamine, the force of heart contraction increased 150 percent in all the patients. However, in the group treated with Viagra, the increased heartbeat was slowed by 50 percent.

"Viagra puts a brake on the effect of dobutamine," Kass said. "It reduces the stimulation of the heart so that the contraction of the heart was less strong." He said the research sets the stage for more specific studies of its use to treat heart problems

However, Kass added that the study also shows that Viagra helps control heart function only when the heart is under stress, and has little impact under normal conditions.

重点词注释

Viagra: sex drug, normally used to treat impotence
Dobutamine: can increase heart rate and pumping strength
placebo: injection with no medical function