title: Has morphine a physiological function in the animal kingdom?
mesh_terms: D000818:Animals; D004723:Endorphins / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives / Q000378:metabolism; D009020:Morphine / Q000502:physiology*; D011957:Receptors, Opioid / Q000378:metabolism*
chemical_list: D004723:Endorphins; D011957:Receptors, Opioid; D004744:Enkephalin, Methionine; D009020:Morphine; C039700:adrenorphin