Effects of hemicholinium-3 and sodium ions on choline uptake system in excised superior cervical sympathetic ganglia of rats

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Abstract
Active choline uptake by rat superior cervical sympathetic ganglia (SCG), which contain abundant cholinergic nerve terminals, was studied with respect to sensitivity to inhibition by hemicholinium-3 (HC-3) and dependence on extracellular Na+ under standard conditions of assay. Choline was taken up by a single saturable process with apparentK m=3.07×10−5 M and Vmax=286 pmoles/min/mg protein. Neither denervation followed by degeneration of cholinergic nerve terminals nor axotomy with successive neuronal degeneration significantly decreased in choline uptake by the ganglia in vitro. HC-3 dose-dependently inhibited ganglionic choline uptake more effectively at lower than at higher choline concentrations. HC-3 sensitive inhibition of ganglionic choline uptake was not seen in young rats one week after birth but appeared with maturity, attaining approximately 50% maximal inhibition in adult SCG. Extent of inhibition by HC-3 and Na+ dependence of ganglionic choline uptake was not altered by denervation or axotomy.