These and other signs of CDS are usually progressive, eventually producing serious behavioral problems that may be intolerable for the owner. At this point, tremendous stress is placed on the human-animal bond. The pet has been a beloved member of the family for 10 or more years, but the changes occurring with CDS may cause the pet owner to consider euthanasia. Without going beyond the scope of this space, let's look briefly at what is thought to be happening biochemically in the brain of a dog with cognitive dysfunction. One of the main changes in the brain of older animals is a decrease in the activity of neurotransmitter chemicals, especially dopamine.
Dopamine is a neurotransmitter necessary for normal cognitive function.
In some older dogs, MAO levels are increased, producing a corresponding decrease in dopamine activity. In addition, some of the byproducts of MAO activity on dopamine are thought to be injurious to brain cells. It is thought that increased MAO activity may be responsible for some of the changes seen in patients with cognitive dysfunction. The exciting new development in the treatment of older patients with cognitive dysfunction involves the use of the drug selegiline, marketed in the United States by Pfizer under the trade name Anipryl. Anipryl is a monoamine oxidase inhibitor.