Endogenous opiates.
D000818:Animals; D004723:Endorphins / Q000502:physiology*; D004745:Enkephalins / Q000502:physiology; D006801:Humans; D010455:Peptides / Q000502:physiology*; D051381:Rats; D011957:Receptors, Opioid / Q000502:physiology
D004723:Endorphins; D004745:Enkephalins; D010455:Peptides; D011957:Receptors, Opioid