The calcium–magnesium interaction in the process of release of noradrenaline by nicotine

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Abstract
The calcium–magnesium (Ca2+–Mg2+) interaction in the process of nicotine-induced release of [3H]noradrenaline ([3H]NA) from rat isolated vas deferens was studied. Increasing extracellular concentrations of Mg2+ caused a dose-dependent depression of release of [3H]NA by nicotine, and this inhibitory effect of Mg2+ was overcome by raising the concentration of Ca2+. It is concluded that Mg2+ antagonizes the nicotine-induced increase in the Ca2+ influx into the adrenergic nerve terminals, and that nicotine acts on adrenergic neuronal membrane rather than intraneuronally to cause release of NA.