The Journal of Neuroscience just published a new study that is particularly interesting in light of recent reports that marijuana may effectively substitute for abuse of more dangerous drugs. In the new study, rats were taught to self-administer heroin and conditioned to associate that behavior with a light that flashed on above the lever that dispensed the heroin. At various stages in the procedure, some of the rats were treated with cannabidiol (CBD), a cannabinoid that doesn’t make you high, but…