DIFFERENCES IN AMINE STORAGE IN RAT HEART AND BRAIN

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Abstract
1 The characteristics of storage of amphetamine-releasable amine in rat heart and brain were studied in vitro with labelled and unlabelled metaraminol ([3H]-MA and MA). 2 In one series of experiments, heart and brain slices were incubated with [3H]-MA prior or subsequent to incubation with the same concentration of MA. 3 When brain slices, thus treated, were subjected successively to field stimulation and to amphetamine, it was found that the ratio of [3H]-MA release by field stimulation to release by amphetamine was dependent upon the order in which brain tissue was exposed to [3H]-MA and MA. 4 With heart slices, on the other hand, the field stimulation/amphetamine ratio of [3H]-MA release remained the same whether the tissue was exposed to [3H]-MA before or after MA. 5 The (+)-isomer of amphetamine released three to four times more [3H]-MA from brain slices than did the (–)-isomer, while the isomers were equipotent with regard to [3H]-MA release from heart slices. 6 Amphetamine-induced [3H]-MA release from heart slices was unaffected by the presence of α-methyl-p-tyrosine, while release from brain slices was inhibited. 7 On the basis of the foregoing results it appears that amine storage differs in brain and heart, with brain exhibiting more than one functional amine pool.