http://www.sciencedaily.com/releases/2009/...90803123240.htm

'Memory loss associated with marijuana use is caused by the drug’s interference with the brain’s natural protein synthesis machinery, according to a study published in Nature Neuroscience.

Though it has been documented that marijuana impairs memory, the precise mechanism for this memory impairment was previously unknown. Andrés Ozaita, of the Universitat Pompeu Fabra in Spain, along with colleagues in France and Germany, focused on THC, the main psychoactive chemical compound in marijuana, which acts on a specific class of receptors known as cannabinoid receptors. These receptors are known to affect the connection strength between neurons.

The scientists found that THC increases the activity of a pathway that promotes protein synthesis in the mouse brain. This transient increase of protein synthesis was mediated specifically by cannabinoid receptors expressed on the brain’s inhibitory neurons, and correlated with long-term memory deficits in mice. Interestingly, the authors also found that inhibition of this signaling pathway by rapamycin, an immunosuppressant drug used to prevent organ rejection following transplantation, prevents THC-induced amnesia in mice.'