Material/Methods: The presence of endogenous morphine and codeine was investigated by Gas Chromatography/ Mass Spectrometry (GC/MS) in the brain of non human primate. The release of endogenous morphine from monkey brain slices was studied in vitro in the presence of high potassium concentrations with and without calcium in the medium.Results: Endogenous morphine, and its direct precursor codeine, was for the first time detected by GC/MS in the brain of non human primate. High potassium concentrations depolarized neurons releasing endogenous morphine twofold above basal line levels in a calcium dependent mechanism.Conclusions: This finding confirms the presence of the endogenous alkaloid throughout the phylogenesis of the nerve system of mammals and lower animals and indicates that endogenous morphine might function as a neuromodulator/neurotransmitter agent in the central nervous system (CNS) of non human primates.

Keywords: Brain - drug effects, Brain - metabolism, Brain Chemistry - drug effects, Cercopithecus - metabolism, Codeine - analysis, Codeine - metabolism, Codeine - pharmacology, Gas Chromatography-Mass Spectrometry, Morphine - analysis, Morphine - metabolism, Morphine - pharmacology, Brain - metabolism, Brain Chemistry - drug effects, Cercopithecus - metabolism, Codeine - pharmacology, Gas Chromatography-Mass Spectrometry, Morphine - pharmacology