Comparison of 3H-spiperone binding in caudate nuclei of rabbits and rats

3H-Spiperone binding and inhibition by competing ligands were studied in caudate nucleus homogenates from Sprague-Dawley rats and New Zealand albino rabbits. 3H-Spiperone binding sites were very similar in the two species and had pharmacological profiles characteristic of D2-dopamine receptors, in accordance with previous reports. However, differences occurred between the species in the potencies with which dopaminergic ergots and other drugs interacted with these binding sites and with regard to the compounds used to define specific binding. These findings suggest that slight differences in relative proportions of subtypes of 3H-spiperone binding sites, or of neuroleptic potencies at these subtypes, may exist between rabbits and rats.