Anxiety: a boost to learning? – methyl-beta-carboline-3-carboxylate as memory-enhancing drug
Anxiety: A boost to learning?
Benzodiazepine tranquilizers such asdiazepam (Valium) enjoy continued popularity despite evidence that they can cloud memory for recent events (see “Stolen Moments,’ July 1986). Now, new compounds that work like Valium in reverse–causing anxiety while boosting memory–have attracted the attention of behavioral scientists, who are working to separate the memory-enhancing effects from the undesired anxiety.
One of these new compounds,known as beta-carbolines, is methylbeta-carboline-3-carboxylate (beta-CCM). In high doses, beta-CCM can cause convulsions in animals. And in humans, beta-CCM quickly becomes anxiety-provoking as the dose increases. Two out of five people who took beta-CCM became extremely agitated, and one became so frightened that he had to be given a benzodiazepine, which quickly counteracted the effects of beta-CCM.
A low dose of beta-CCM given justbefore a training session, however, appears to allow animals to learn better than do undrugged animals, report French scientists Patrice Venault and Georges Chapouthier and colleagues. The undrugged animals, in turn, remember their training better than do animals given diazepam.
In one of their experiments, the researchersexamined the effects of beta-CCM on the ability of mice to remember a new location. Hungry mice normally eat very little in a new environment, but will eat freely once they’ve had a chance to familiarize themselves with it, however briefly. Beta-CCM given before a 30-second exposure to a new cage aided mice in recalling the cage four days later well enough to eat there. Mice given diazepam before training forgot having been in the new cage and ate much less when reintroduced to the cage. Undrugged mice ate an amount intermediate between the two test groups.
Beta-CCM-treated mice also excelledin remembering not to venture into an area where they had previously been punished by electric shock. Their ability to restrain themselves when appropriate suggests that beta-CCM’s effects are not due to a nonspecific increase in activity, but represent real learning.
In a different kind of learningtask, newborn chicks were given beta-CCM and then exposed to a moving decoy. The next day, the chicks who had had beta-CCM spent more time following the decoy than did untreated chicks. Presumably they learned and remembered the appearance of the decoy better due to beta-CCM.
In an effort to separate the memory-enhancingproperties of the drug from the anxiety-producing ones, chemists have been fabricating variations on the beta-carboline theme, but have had no success thus far. “It may prove impossible to separate the two,’ Chapouthier says. “It may be that you need some anxiety in order to learn.’
These experiments support findingsby other reserchers showing that diazepam impairs memory by reducing alertness. Beta-CCM, on the other hand, increases alertness, letting animals learn and remember new experiences better.
COPYRIGHT 1986 Sussex Publishers, Inc.
COPYRIGHT 2004 Gale Group