Regulation by Cations of [³H]Spiroperidol Binding Associated with Dopamine Receptors of Rat Brain

The effects of monovalent and divalent cations on binding of [ 3 H]spiroperidol to dopamine receptors in rat corpus striatum were studied. Both monovalent and divalent cations as well as several chelating agents increase the number of [ 3 H] spiroperidol binding sites. Manganese is most potent, enhancing binding at 1 μ m concentration, while magnesium and calcium are at least two orders of magnitude less potent and the monovalent cations sodium, potassium and lithium are still weaker. Divalent cations enhance the potency of dopaminergic agonists in competing for [ 3 H]spiroperidol binding, an effect which appears to be independent of the ionic augmentation of [ 3 H]spiroperidol binding. Divalent cations decrease both the association and dissociation rates of [ 3 H]spiroperidol binding to dopamine receptor sites.