Marijuana and Memory

This time of year, memory is on everybody’s minds. With late night cramming and early morning panicking – ‘tis the season of exams. So with all this stress you may want dabble with various calming chemicals – rescue remedy, copious amounts of tea and cigarettes, perhaps all with dash of alcohol, and maybe a shneaky shmoke, but is that actually a good idea?

Mary-jane, gunja, weed, pot, whatever you call it, research shows that marjiuana significantly impairs working memory – the memory that you would need to use to cram in those last minute facts about Chaucer or Freud or Boyle. But until recently, it was not clear exactly what the source of the memory lapses were.

The major psuchoactive ingredient (THC) impairs memory independently of its direct effects on neurons. The side effects stem instead from the drug's action on astroglia, which are passive support cells to neurons in the brain supporting, protecting and feeding neurons. Support cells typically help the propagation of electrical signals along neural cells.

It was actually thought that that was all that the astroglial cells do – support. But now evidence has accumulated that suggests these cells play a more active role in forging connections between one neuron and another.

The researchers didn't set out to discover how marijuana causes its cognitive side effects. Rather, they wanted to understand the receptors found on the cells. Mice lacking these receptors on the astroglial cells are protected from impairments to spatial working memory that would usually follow a dose of THC. These receptors are found on other neurons as well, yet if the receptors are lacking in only in neurons, then the mice still suffer the memory problems.

"The study shows that one of the most common effects of cannabinoid intoxication is due to activation of astroglial receptors," the researchers wrote.

Given that different cell types express different variants of that receptor, there might be a way to therapeutically activate the receptors on neurons while leaving the astroglial cells out. Thus, these findings offer important new insight into the brain and raise the possibility that marijuana's benefits for the treatment of pain, seizures and other ailments might someday be attained without hurting memory, the researchers say.

The findings further suggest that astrocytes might be playing unexpected roles in other forms of memory in addition to spatial working memory, Zhang said. The researchers hope to explore the activities natural endocannabinoids (things that are like cannabis), which naturally trigger the receptors, on astroglial and other cells. The endocannabinoid system is involved in appetite, pain, mood, memory and many other functions. "Just about any physiological function you can think of in the body, it's likely at some point endocannabinoids are involved," Marsicano said.

And that means an understanding of how those natural signalling molecules act on astroglial and other cells could have a real impact. For instance, Zhang said, "we may find a way to deal with working memory problems in Alzheimer's."

But back to the marijuana effects – it is clear that this drug triggers memory impairment, so perhaps it would be best to stave off the stuff for a while, and give your astroglial cells a rest!