Histochemical and Biochemical Observations on the Effect of Reserpine on Noradrenaline Storage in Vasoconstrictor Nerves

Abstract Tissue sections of cat skeletal muscle were analysed for adrenergic fibres by a specific histochemical fluorescence technique. Fibres with green fluorescence and varicosities typical of adrenergic fibres were seen almost exclusively surrounding the external muscular layer of the small arteries in the tissue. No adrenergic nerve fibres could be detected after postganglionic sympathetic denervation of the muscles. Reserpine (5 mg/kg i.v.) caused a complete disappearance of the fluorescence of the fibres within a few hours after administration. Decentralization of the sympathetic nerves to the muscles prevented the fibres from losing fluorescence after reserpine. An infusion of noradrenaline 24 hours after reserpine administration caused a reappearance of fluorescent nerve fibres of practically normal appearance. A certain amount of noradrenaline could be detected by biochemical assay both in decentralized muscles 5 to 9 hours after reserpine administration and in muscles from reserpine‐treated animals in which noradrenaline had been infused. The data support the view that a small amount of noradrenaline can be retained in adrenergic nerves by mechanisms which are resistant to the effect of reserpine.