Use of [3H] Spiperone for Labelling Dopaminergic and Serotonergic Receptors in Bovine Caudate Nucleus

Abstract

[3H]Spiperone binding was used to study neurotransmitter receptors in bovine caudate nucleus in displacement and saturation binding experiments. Displacement curves for several antagonists are biphasic and can be analyzed into contributions from dopaminergic and serotonergic sites. Antagonist binding at each class of sites follows the simple mass action equations for binding at a homogeneous set of sites (slope factors close to unity). Agonist displacement curves also indicate complex behavior, but agonist binding to the dopaminergic sites alone exhibits heterogeneous properties (slope factors less than unity). Saturation binding experiments were conducted on each class of site, defining dopaminergic binding of [3H]spiperone as that binding displaced by 0.1 mM dopamine and serotonergic binding as that displaced by 0.3 .mu.M mianserin. In each case, a single class of binding sites was detected: the binding parameters derived in this way were used to calculate the proportions of the 2 classes of binding site observed in displacement experiments. Good agreement was obtained between calculated and observed values.