How marijuana impairs short-term memory
Scientists have discovered how marijuana makes you forget.
The finding could help researchers develop drugs that have the same therapeutic benefits but with fewer memory effects. Nature News reports.
The drug impairs working memory – the ability to retain and use information over short periods of time, like phone numbers or people’s names. Turns out, this side effect occurs because of a previously unknown mechanism between neurons and non-neuronal cells called astrocytes.
It was thought for a long time that these star-shaped brain cells were purely to support and protect neurons. BUT, according to the new work, astrocytes control neurons and memory.
“The supporting actor has become the leading actor,” says study researcher Xia Zhang of the University of Ottawa Institute of Mental Health Research.
Their methods are hefty, and here are some things to know:
Marijuana’s psychoactive ingredient is tetrahydrocannabinol (THC).
Structures called cannabinoid type 1 (CB1) receptors interact with THC in the brain; these receptors are found on neurons and astrocytes.
- Using tiny electrodes implanted into rat brains, they found that THC weakens the connections (or synapses) between neurons and the hippocampus, the part of the brain crucial for forming memories.
- Then they repeated the experiment in 2 types of GM mice that lacked CB1 receptors on their neurons. THC weakened their synapses as well.
- On the other hand, THC had no effect on the synapses in GM mice who lacked the receptor on their astrocytes.
- They tested all 3 types of mutant mice with a working-memory task: to remember the location of a submerged platform in a water maze. THC impaired the performance of mice lacking the CB1 receptor on neurons but not in mice lacking the receptor on astrocytes.
In other words, marijuana impaired working memory only when it was able to bind to astrocytes, Scientific American explains.
The findings could eventually lead to THC-related drugs that specifically target the receptors on some brain cells and not others. Such compounds might have therapeutic effects, for example as painkillers, without affecting the function of working memory.
The work was published in Cell yesterday. Via Nature News.
Image by gourabstock via Flickr
This post was originally published on Smartplanet.com