The effect of colchicine treatment on the buoyant density of noradrenaline storage particles in the rabbit superior cervical ganglion.

The subcellular distribution of noradrenaline (NA) was studied in the rabbit superior cervical ganglion before and after colchicine treatment. One-third of the total NA could be sedimented with the microsomal material in control conditions. Upon colchicine treatment the percentage of the NA which was particle-bound increased only slightly. The absolute NA content of the superior cervical ganglion from colchicine-treated rabbits, however, showed a 3.5-fold increase compared to control animals. Density gradient centrifugation of the microsomal fraction revealed that the distribution of the NA-containing particles changed significantly. Before colchicine treatment the NA was found in a broad band covering the gradient fractions where 'light' and 'heavy' NA vesicles were expected to equilibrate. After colchicine treatment the NA was concentrated in the 'heavy' NA vesicles part of the gradient. The dopamine beta-hydroxylase activity and the NA content in the gradient are increased 3 times after colchicine treatment. These experimental results can be explained by the axoplasmic transport impairing action of colchicine. The neuronal cell body accumulates 'heavy' NA vesicles formed there, unable to transport them towards the periphery.