This was written back in 2008, but I don't think this has been mentioned on the board before, so I thought I'd post it.
CHICAGO, March 12 (Reuters) - A new class of pain drugs may also interfere with important brain functions like learning and memory, U.S. researchers said on Wednesday.
The finding may have implications for drug development, and it may also help explain some of the psychiatric side effects of the Sanofi-Aventis (SASY.PA) weight-loss pill rimonabant, which is sold in Europe as Acomplia, they said.
The drugs block a specific pain receptor -- a molecular doorway -- known as TRPV1
"We've known that TRPV1 receptors are in the brain, but this is the first evidence of what they do there," Julie Kauer of Brown University in Rhode Island said in a statement.
"And the role we uncovered is unexpected. No one has ever linked these pain receptors to a mechanism strongly associated with memory. So we may have found a whole new player in brain plasticity," said Kauer, whose study appears in the journal Neuron.
TRPV1, or transient receptor potential vanilloid 1, is linked with inflammatory pain. Naturally occurring agents like capsaicin -- which gives chili peppers their kick -- act on this nervous system receptor.
Eli Lilly and Co (LLY.N) , Merck & Co Inc (MRK.N), Pfizer Inc (PFE.N), Wyeth (WYE.N) and others have invested in the development of drugs that block TRPV1 in the hopes of developing a new kind of pain killers.
But research by Kauer and colleagues suggest this pain receptor may also play an important role in other key brain functions.
In experiments on rat brain tissue, they found that TRPV1 regulates a nerve function known as long-term depression, changing the strength of connections between neurons. These changes -- and a related process known as long-term potentiation -- are thought to be the cellular mechanics behind memory making.
Kauer's team found they could block long-term depression using TRPV1 blockers in rat brain tissue. They also could induce this memory function in TRPV1 by using capsaicin.
They also found that rimonabant blocked TRPV1.
"Our findings suggest the possibility that some of the psychiatric side effects from rimonabant could be due to the blocking of TRPV1 receptors," Kauer said.
An advisory panel to the U.S. Food and Drug Administration in June recommended that rimonabant not be approved because it may increase suicidal thoughts and depression.
Kauer said the findings also suggest potential new targets for drugs to prevent memory loss or possibly treat neural disorders such as epilepsy. (Editing by Maggie Fox and Cynthia Osterman).
