Accumulation and loss of noradrenaline central to a constriction on adrenergic nerves

Noradrenaline accumulation and fluorescence intensity central to a contriction were measured at different time intervals after constriction of cat splenic nerves. After 4 days noradrenaline had increased some seven times and fluorescence intensity some twenty times. The latter appears to give a more sensitive measure of noradrenaline accumulation. The high levels of noradrenaline and fluorescence intensity were not maintained, but declined towards normal values at 21 days. The decline could not be explained by either release of noradrenaline by nerve impulses or intra-axonal destruction of noradrenaline by monoamine oxidase. The inability to accumulate noradrenaline above a second, later constriction made when chromatolysis was fully established, suggests that the decline may be due to changes in the synthetic activity of the perikaryon. The time course of the accumulation and loss of noradrenaline was similar to those of dopa-decarboxylase and monoamine oxidase. Unexpectedly, the rate of accumulation of noradrenaline was linear throughout the 4-day period to peak levels of noradrenaline.