Endorphinsbeta-Endorphinbeta-LipotropinAdrenocorticotropic HormoneMelanocyte-Stimulating HormonesPituitary Hormones, AnteriorPro-OpiomelanocortinN-Terminal AcetyltransferasesPituitary GlandEnkephalinsNaloxoneProtein PrecursorsRadioimmunoassayHistamine ReleaseCalciumDelayed-Action PreparationsRyanodine Receptor Calcium Release ChannelCells, CulturedNeurotransmitter AgentsKineticsVirus ReleaseRats, Sprague-DawleyDose-Response Relationship, DrugTime Factors