For FlamingLiberalMulticulturalist: regarding cannabinoid receptors and receptor antagonists:
The last one deals with antagonists causing immediate withdrawal symptoms. Similarly there are also opioid receptor agonists (ie morphine) and opioid receptor blocking agents (ie naltrexone). Giving naltrexone to a morphine dependent person would be medically catastrophic and very cruel. Alcohol is a general CNS depressant and thus there is no specific "ethanol receptor".