Noradrenaline Storage, Release, and Inactivation in Sympathetic Nerves

• Published in: Circulation research 1967-12, Vol.21 (6 Suppl III), p.III-57-III-61
• Main Author: Geffen, Laurence B
• Format: Article
• Language: English
• ISSN: 0009-7330; 1524-4571

Evidence that sympathetic nerves take up and re-use the transmitter they liberate has been examined. Their capacity to liberate noradrenaline during repeated stimulation was shown to depend primarily on the size of the fraction which escapes recapture by overflowing into the circulation. This loss could be increased either by higher frequencies of stimulation or by the use of phenoxybenzamine to block uptake, both of which produced an accelerated decline in liberation.Noradrenaline in the spleen was expressed not as a tissue concentration, but in terms of deoxyribonucleic acid (DNA), which is independent of the organʼs blood content. Nerve stimulation at 30 per second for up to 5 minutes produced a small nonprogressive depletion of 8%, which was increased to 28% in the presence of phenoxybenzamine. These losses could be accounted for as overflow into the venous blood. The results indicate that about one third of the noradrenaline was readily available for release and that some 70% of the liberated transmitter was rebound.Decentralization of the spleen by section of its preganglionic nerve supply resulted in a 38% increase in noradrenaline stores, which could account for the increased amounts liberated when the nerves were subsequently stimulated. This suggests that reflex activity can reduce the level of transmitter stores in sympathetic nerves.