Control of Noradrenaline Release from Hippocampal Synaptosomes

Abstract Potassium-evoked tritiated noradrenaline (NA) release from hippocampal synaptosomes was measured with a superfusion method. A single 2-min high-K⁺ pulse released 39% of the vesicular NA by a Ca²⁺-dependent mechanism; the Ca²⁺-independent release was negligible. After changing the vesicular NA store size by pretreating rats with either α-methyl-para-tyrosine, 500 mg/kg, or tranylcypromine, 10 mg/kg, a single K⁺ pulse released a constant percentage of the vesicular NA. With two K⁺ pulses, however, there was a reduction in the percentage of vesicular N A released in response to the second pulse.