If a specific phenotype is needed, please let us know which one. Representative population, High vs. low with a median split, top/bottom quartile, or specific behavioral features. Example of dependent variables include: responding under fixed ratio, progressive ratio, response despite quinine adulteration, time-out responding, composite addiction index, withdrawal-induced hyperalgesia, loss of righting reflex, tolerance, sensitivity to naltrexone, acamprosate, disulfiram.