Sexual impotence was long thought to be a psychological problem, a theory that helped line the pockets of countless therapists. Now scientists know that in most cases the cause is in the body, not the brain. Last week researchers from the Clark Urology Center at the University of California, Los Angeles, reported in The New England Journal of Medicine that they had for the first time identified the chemical that plays a key role in producing erections. It's a substance called nitricoxide-and lack of it, says urologist Dr. Jacob Rajfer, chief author of the new study, could conceivably be responsible for the type of impotence that plagues over 7 million American men.
Nitric oxide is manufactured throughout the body, playing a role in memory and immune response. Its function in erections, the Los Angeles team discovered, is to relax the smooth muscles of the penis, which in turn allows blood vessels in the organ to enlarge and fill. Rajfer and his colleagues demonstrated this effect in the lab, using samples of penile muscle tissue taken from men who were having surgery for penile implants. Even though these volunteer subjects were themselves impotent (from causes including diabetes, hypertension, severe atherosclerosis and prostate surgery), the experiments on their tissue proved only that nitric oxide could relax the muscle. In subsequent work published last year, Rajfer and urologist Dr. Tom Lue of the University of California, San Francisco, showed that nitric oxide could produce erections in dogs, rats and monkeys.
The researchers believe their new knowledge of nitric oxide's role in erections will pave the way for its use in more effective treatments for impotence. Since the mid-1980s, thousands of men have found relief from the condition by injecting themselves with one of three drugs: papavarine, prostaglandin E1 and phentolamine. But some men can't bear to stick needles into their penises, says Rajfer, and the treatment sometimes causes uncomfortably prolonged erections, or headaches and faintness. In the past these drugs were prescribed without specific understanding of how they worked; now researchers believe they enhance the production or effect of nitric oxide. That information, says Rajfer, will help scientists reach their goal-perhaps within a decade-of a more convenient pill or skin patch to restore potency.