by Phil Williams

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If you need another reason to just say no, consider a rat on drugs.

Laboratory rats given a synthetic compound similar to marijuana’s active ingredient quickly lose their perception of time, a clear indication that the drug has a direct affect on attention span, according to research by a trio of University of Georgia researchers.

“In the real world, this suggests that someone smoking marijuana might well be able to do a task briefly, but over time there could be serious attention problems,” said psychologist Jonathon Crystal, who led the study.

Routine tasks such as driving, which require sustained attention span, are therefore risky under the influence of a “cannabinoid” compound like marijuana, he said.

In their study, Crystal and his colleagues, Andrea Hohmann, an assistant professor of psychology, and Kenneth Maxwell, the laboratory research coordinator, placed rats in a box equipped with an audio speaker and two levers. Over time, the rats were trained to get food pellets by pressing one lever whenever the speaker issued a long sound, 16 seconds, and another lever during a short 4-second sound.

Then the researchers gave the rodents a synthetic form of THC, or tetrahydrocannabinol, the active ingredient in marijuana, or Cannabis sativa. Rats “under the influence” had difficulty distinguishing between the long and short sounds, even though they had performed the tasks perfectly before.

Using computer models to interpret the data, the scientists found that the rats ability to maintain attention was altered by exposure to the drug through a specific brain receptor mechanism.

The cannabinoids produce a substantial decline in sensitivity to time through a specific brain receptor mechanism, Crystal said.

The study, funded by a grant from the National Institute on Drug Abuse, was published in the journal Behavioural Brain Research.

For more information, contact Jonathon Crystal at jcrystal@uga.edu; Andrea Hohmann at ahohmann@uga.edu; or Kenneth Maxwell at kmaxwell@egon.psy.uga.edu; or access www.uga.edu/animal-cognition-lab.

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