Autoradiographic study of the rat vas deferens incubated with 3H-noradrenaline

Rat vasa deferentia were incubated with 0.2 μmol/l 3H-noradrenaline for 60 min and then washed out with amine-free solution for 100 min. Autoradiography then revealed a preferential labelling of the varicosities in the immediate vicinity of the surface of the tissue. However, when tissues were obtained from reserpine-and pargyline-pretreated rats (to block vesicular uptake and monoamine oxidase), 3H-noradrenaline was able to penetrate more deeply into the tissue. These differences are in accordance with the view that the autoradiographs reflect the 3H-noradrenaline concentration gradient (within the extracellular space) generated by the neuronal uptake of the 3H-amine; the concentration gradient is steeper (and the heterogeneity of labelling is more pronounced) in tissues with intact vesicular uptake and monoamine oxidase than in tissues in which these mechanisms had been inhibited.