[opioid peptides].
D000700:Analgesics; D000818:Animals; D001921:Brain / Q000378:metabolism*; D004723:Endorphins / Q000145:classification / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism
D000700:Analgesics; D004723:Endorphins; D011957:Receptors, Opioid