Pot's Active Ingredient Could Fight Alzheimer's - more at Forbes.com" The active ingredient in marijuana -- delta-9- tetrahydrocannabinol (THC) -- may slow the progression of Alzheimer's disease, new research suggests.

According to a team at the Scripps Research Institute in La Jolla, Calif., THC preserves brain levels of an important neurotransmitter called acetylcholine. It does so by inhibiting the enzyme acetylcholinesterase, which breaks down acetylcholine.

Reporting in the current issue of Molecular Pharmaceutics, the Scripps team noted that existing Alzheimer's medicines, including donepezil and tacrine, also relieve symptoms by inhibiting this enzyme.

In their work in the laboratory, the researchers found that THC inhibits a different site on the acetylcholinesterase molecule and at lower concentrations.

They also discovered that THC prevents the formation of amyloid protein plaques that damage the brain and are a hallmark of Alzheimer's disease.

"Our results provide a mechanism whereby the THC molecule can directly impact Alzheimer's disease pathology," the study authors wrote. In addition, THC may prove valuable as a model for developing new and more effective drugs to treat the disease, they said."