Cummings also found the plaques in the brains of three cats during autopsies. One was going in a closet and couldn't find its way out. One cat would no longer go up and down stairs and seems to have forgotten how. Some researchers suspect that dogs with cognitive dysfunction also suffer from inefficient use of dopamine, a brain chemical that transmits messages among nerves. Anipryl is a version of a drug called L-deprenyl that is used to treat people with Parkinson's disease, who suffer from a shortage of dopamine.
Veterinarians make the diagnosis by ruling out other problems that cause similar symptoms.
In the clinical trials, Anipryl basically reversed most of the symptoms of cognitive dysfunction, said Landsberg, the Ontario veterinarian who conducted some of the trials. About 20 to 25 percent of the dogs on Anipryl in the trials vomited or had diarrhea, compared with 10 to 20 percent of those who got placebos, Ruehl said. Some dogs also exhibited behavior changes. Most dogs that experienced side effects had only mild side effects that went away quickly, Ruehl said. Landsberg has used Anipryl in about 20 cats and found it helpful.