[3H] clonidine binding to rat hippocampal membranes.

Alpha adrenergic receptor subtypes in rat hippocampal membranes were studied, using [3H] clonidine as the radioactive ligand. On the basis of competitive binding studies, using the selective antagonist-prazosin, WB-4101, and yohimbine, [3H] clonidine appeared to bind to a population of presynaptic sites that are pharmacologically similar to receptors previously classified as alpha 2. A computerized model that linearized and produced the best possible fit to the experimental data points indicated that [3H] clonidine binds to a single population of receptors possessing equal affinity for the ligand. Binding data also indicated that rat hippo-campus contains significantly fewer [3H]clonidine binding sites than rat cortex.