Direct Studies on the Disappearance of the Transmitter and Changes in the Uptake‐Storage Mechanisms of Degenerating Adrenergic Nerves

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Malmfors, T. and Ch. Sachs.Direct studies on the disappearance of the transmitter and changes in the uptake‐storage mechanisms of degenerating adrenergic nerves. Acta physiol. scand. 1965.64. 211–223. – The histochemical fluorescence method of Falck and Hillarp has been applied to a study of the disappearance of the endogenous noradrenaline (NA) and the uptake‐storage mechanisms of the adrenergic nerves in the rat iris during the course of degeneration following axotomy. It was found that the transmitter stored in the terminals does not disappear gradually but quite suddenly and with various times of onset for the different systems of terminals. The uptake and accumulation of NA and α‐methyl‐NA were examined in untreated and reserpinized animals. These experiments show that the uptake‐storage mechanisms in any given system of terminals operate up to a certain time without any obvious changes, but then deteriorate rapidly, at about the same time as the transmitter stores disappear. The axon membrane reabsorption mechanism seems to be lost somewhat prior to the storage mechanism of the transmitter granules, at the same time as degenerative changes seem to occur in the axon membrane, making possible a passive leakage of NA. – The results add further weight to the view that the cocaine‐like component in the denervation supersensitivity is due to the loss of the uptake mechanisms. – Following the administration of bretylium the degenerative processes were delayed for about 8 hrs.

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