title: Are there opiate receptors in the invertebrates?
mesh_terms: D000818:Animals; D002490:Central Nervous System / Q000187:drug effects / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D004745:Enkephalins / Q000494:pharmacology; D006372:Helix, Snails / Q000187:drug effects* / Q000378:metabolism; D006719:Homovanillic Acid / Q000378:metabolism; D009270:Naloxone / Q000494:pharmacology; D011957:Receptors, Opioid / Q000378:metabolism*
chemical_list: D004745:Enkephalins; D011957:Receptors, Opioid; D009270:Naloxone; D004298:Dopamine; D006719:Homovanillic Acid