A study involving rats reveals the mechanism responsible for learning impairment due to liver failure and shows that sildenafil restores cognitive function.
Liver disease sometimes causes hepatic encephalopathy, which involves brain damage, personality changes, and intellectual impairment due to hyperammonemia (high levels of ammonia in the blood). However, the mechanisms involved in both learning and how liver disease leads to learning impairment are unclear.
In a new study led by Vicente Felipo of the Laboratory of Neurobiology at the Fundacion Valenciana de Investigaciones Biomedicas in Valencia, Spain and published in the February 2005 issue of Hepatology, researchers hypothesized that impaired learning was due to a defect in the glutamate- nitric oxide-cGMP pathway in the brain and that administering sildenafil to increase cGMP would restore learning ability. Sildenafil, commonly known as Viagra, is known to prevent the destruction of cGMP and allow it to accumulate in the body.
Hepatology, the official journal of the American Association for the Study of Liver Diseases (AASLD), published by John Wiley & Sons, Inc. is available online via Wiley InterScience.
Researchers examined four groups of rats in their study: