title: Calcium-opiate antagonism in the periaqueductal grey (PGA) region.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002535:Cerebral Aqueduct / Q000187:drug effects*; D004723:Endorphins / Q000037:antagonists & inhibitors*; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives*; D004745:Enkephalins / Q000037:antagonists & inhibitors; D008297:Male; D009020:Morphine / Q000037:antagonists & inhibitors*; D009619:Nociceptors / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D004745:Enkephalins; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; C022118:enkephalinamide-Met, Ala(2)-; D009020:Morphine; D002118:Calcium