Noradrenaline uptake and fluorescence histochemistry in bovine splenic nerves.

A combination of fluorescence histochemical and radiometric methods was used to study the uptake and accumulation of exogenous noradrenaline in the non-terminal sympathetic axons of isolated bovine splenic nerve trunk. Non-incubated nerve fibers mostly showed a low fluores cence intensity, but a few fibres exhibited very strong fluorescence with a beaded appearance. The number of beaded axons could be increased by incubation, especially with a-methyl-nor-adrenaline. After incubation, even in amine-free media, fluorescent material accumulated near the cut ends and also close to areas accidently compressed during the preparation. The results suggest that transport of noradrenaline had occurred under the experimental conditions. In cubation with noradrenaline, particularly after inhibition of monoamine oxidase, or with a-methyl-noradrendine, resulted in a strong concentration-dependent increase of the fluores cence intensity, even in the presence of reserpine. Under the experimental conditions the tissue/ medium ratio was found to be about 60, using 10-6 M racemic 3H-noradrenaline in the in cubation medium. It is concluded that the sons of the bovine splenic nerve trunk possess a reserpine-resistant mechanism for concentrating noradrenaline which is qualitatively similar to, but quantitatively considerably less efficient than, that previously observed in nerve terminals in other tissues and species.