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For 2 years, Gary Lynch and his colleagues have been watching rats in their labs-under the influence of a new class of drugs-learn remarkably quickly to navigate new mazes. As they watched, the researchers also wondered: Do the new drugs give rats extraordinary memory, or do they simply make the rats exceptionally alert? The distinction is crucial, because if the former turns out to be true, Lynch, a neuroscientist at the University of California, Irvine, and his colleagues have reached a long-sought goal--developing drugs that have profound effects on he molecules that transmit memories.
But it's far from certain that they've reached that goal. The drugs in question are called Ampakines and bind to neurotransmitter receptor molecules on neurons in the brain. The molecules are called DL-alpha-amino-3-hydroxy-S-methyl-4-isoxazolepropionic acid, or AMPA receptors. And Lynch's results, some of which were published in January in the Proceedings of the National Academy of Sciences (another paper is due out next month) have aroused both interest and criticism. The interest stems from neuroscientists' desire to find compounds that can improve memory in a meaningful way. "This type of memory-enhancing drug could be very beneficial" for people in the early stages of Alzheimer's disease and other forms of dementia, says Steven Younkin, an Alzheimer's disease researcher at Case Western Reserve University in Cleveland. Other memory-enhancing drugs on the market which affect either AMPA receptors or the excitatory neurotransmitter acetylcholine have had little impact in treating memory disorders.
The criticism, however, stems from worries that Ampakines too have their limits. Younkin hastens to add that Ampakines "are not going to cure Alzheimer's," as they won't affect the neural degeneration that is the hallmark of the disease. Beyond that, critics say there's a chance the drugs won't have much of an effect on memory and learning at all: Ampakines' mode of action in the brain appears analogous to that of caffeine, which does affect learning, but only to a small degree. "And you wouldn't expect much from giving caffeine to an Alzheimer's patient," says one neuroscientist.
It wasn't the clinical uses of Ampakines, however, that originally sparked the interest of Lynch and a number of other researchers who have investigated them, such as Ursula Staubli and Joseph LeDoux of New York University (NYU)...