October 30, 2008

Viagra Fights Fatigue

Feeling tired? Researchers say Viagra could help alleviate your fatigue.

A team at the University of Iowa found the drug helped animals with the mislocalized enzyme called neuronal nitric oxide synthase (nNOS).

They also revealed a difference between the prolonged fatigue after mild exercise in muscular dystrophy patients and the inherent muscle
weakness caused by the disease.

The studies found a faulty signaling pathway that leads to exercise-induced fatigue in mouse models of muscular dystrophy.

Yvonne Kobayashi, Ph.D., led the research and said targeting the signaling pathway could help develop therapies to treat this type of fatigue.

"This is an exciting finding and our research suggests that there probably are many different neuromuscular conditions where fatigue could be treated by targeting this newly discovered pathway," Nature magazine quoted Kevin Campbell, Ph.D., UI professor and head of molecular physiology and biophysics, as saying.

Through animal models, researchers found if nNOS is absent from its normal location on the muscle membrane, then blood vessels do not relax normally and the animals experience post-exercise fatigue.

Campbell said, "Those mice behave just like my patients with Becker muscular dystrophy." As soon as he said that we knew what might be going on, because Becker patients have mislocalized nNOS."

Researchers showed that mice with misplaced or missing nNOS exhibited prolonged fatigue after mild exercise.

The enzyme nNOS makes a signaling molecule called nitric oxide. It triggers the production of a chemical called cGMP, which leads to the relaxation of smooth muscle around blood vessels, which in turn increases the blood flow.


Viagra is designed to increase blood flow and prolongs the existence of the cGMP molecules that promote blood vessel dilation.

The researchers found Viagra could ease fatigue in mice with mislocalized nNOS.

"The mice that have the nNOS mislocalized still have some nitric oxide signaling, but the Viagra enhances that signal by inhibiting PDE and preventing breakdown of cGMP," said Campbell.


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