The distribution in brain of the polyamines spermidine and spermine is described in the rat, dog, sheep, rabbit and in man. The distribution pattern was about the same in all the species, spermidine concentration being highest in areas rich in white matter. The concentration of spermine was lower than that of spermidine and showed less variation from area to area. Rat brain polyamine content was the same in rats killed by decapitation as in those killed by rapid freezing in liquid nitrogen and was also unchanged up to 48 h after the death of the animal.ALTHOUGH the polyamine now known as spermine was once called neuridine it is not generally recognized that spermine and the closely related compound spermidine are present in large amounts in nervous tissue. In recent times interest in the polyamines in brain has been re-awakened and their distribution in some areas of the brain of the rabbit (SHIMIZU, KAKIMOTO and SANO, 1964) , monkey (MICHAELSON, COFFMAN and VEDRAL, 1968), sheep and man (KREMZNER, 1970) has been described. The present communication gives the distribution of the polyamines in rat and dog brain and also gives that in the rabbit, sheep and in man in greater detail than hitherto described. Possible post mortem changes in brain polyamine content were also investigated. MATERIALS A N D M E T H O D SFemale Wistar rats weighing 140-160 g were killed by decapitation (unless otherwise stated) and the brains quickly removed and dissected at room temperature. New Zealand White rabbits weighing 2-2.5 kg were killed by cervical fracture and exsanguinated. The brains were removed and dissected at once. Sheep heads from animals stunned by electric shock and killed by exsanguination were obtained from the local abattoir. Dissection was completed within 12 h of the death of the animal. The dissection of brains from Beagle dogs which had been anaesthetized with thiopentone and killed by exsanguination was completed within 24 h of death. The human brains were also dissected within 24 h of death.Tissue samples weighing up to 1.5 g were homogenized in 5 ml cold 10% TCA in an M.S.E. top drive homogenizer. The homogenate was allowed to stand for 30 min and then centrifuged at 1500 g R E F E R E N C E S

Abstract— Spermidine and spermine are taken up into mouse cerebral hemisphere slices by active transport and can be accumulated well above the medium concentration. The uptake process shows saturation kinetics and resembles that for amino acid uptake in that it is sensitive to temperature and inhibited by cyanide, 2,4‐dinitrophenol or by the absence of glucose from the medium. However, at low initial medium concentrations spermine is taken up by a process which is insensitive to metabolic inhibitors or to temperature. It is suggested that either physical binding to a cellular constituent or exchange transport may account for this uptake. Ouabain does not inhibit polyamine uptake. Spermidine or spermine uptake is inhibited by cadaverine and putrescine. Spermine is the most potent inhibitor of spermidine uptake and vice‐versa. Polyamine uptake differs from that of amino acids in that it is increased by a reduction in medium sodium or calcium content and decreased by an increase in medium potassium content. Recently taken up spermine undergoes heteroexchange with spermidine and homoexchange with recently entered spermine. Spermidine undergoes neither heteroexchange with spermine nor homoexchange.