TAKE A TOKE, MINIMIZE STROKE, RESEARCH SAYS There may be a silver lining in a cloud of marijuana smoke.  While most medical researchers don't condone recreational marijuana use, marijuana derivatives may prevent brain cell damage in strokes.  Researchers at the National Institute of Health, led by A.J.  Hampson, found that cannabidol, one of a class of marijuana constituents called cannabinoids, is a powerful antioxidant.  When tested on rat neurons in a lab dish ( no smoking was involved ) the substance prevented the death of brain cells during conditions simulating a stroke. Another cannabinoid, commonly known as THC, proved to be an equally effective antioxidant and neuron protector.  However, the researchers said THC's euphoric side effects would not allow doctors to administer it in high doses.  The study was reported in the Proceedings of the National Academy of Sciences.