EndorphinsEnkephalin, Methioninebeta-Endorphinbeta-LipotropinNaloxoneNeuropeptidesEnkephalinsReceptors, OpioidAdrenocorticotropic HormoneMelanocyte-Stimulating HormonesReceptors, Opioid, muPituitary Hormones, AnteriorAnalgesics, OpioidPro-OpiomelanocortinReceptors, Opioid, deltaN-Terminal AcetyltransferasesReceptors, Opioid, kappaPituitary GlandOpioid PeptidesProtein PrecursorsRadioimmunoassaySubstance PNarcotic Antagonists