Morphine, the most powerful opiate analgesic drug in opium, acts directly on synapses of the arcuate nuclei within the central nervous system to relieve pain. It is a highly addictive drug, to which tolerance as well as physical and psychological dependences quickly develop. Administered as intravenous, subcutaneous or epidural injections, Morphine creates a profound contraction sensation in the muscles due to histamine release and also produces a "rush" mediated by different receptors in the central nervous system. Morphine is a phenanthrene opioid receptor agonist. By binding to μ opioid receptors within the central nervous system associated with analgesia, sedation, physical dependence and respiratory depression, the euphoric effects of Morphine are quickly followed by withdrawal symptoms.