Abstract

The uptake of norepinephrine into the sympathetic innervation of the isolated rat heart was dependent on the presence of sodium ions in the external medium, but was not affected by the absence of calcium ions. The sodium dependence of norepinephrine uptake is further evidence for the view that this process is mediated by an active transport system in adrenergic nerve terminals. Similar sodium-dependent uptake processes may be present at other chemically transmitting synapses.