Binding studies with the 5-HT1B receptor agonist [3H]CP-96,501 in brain tissues

Binding studies in rat brain membranes have shown that [³H]CP-96,501 is a selective, high affinity radioligand for 5-HT_1B receptors. Additional studies with [³H]CP-96,501 in brain tissues of several other species were undertaken to investigate its utility in detecting this receptor subtype. The presence of 5-HT_1B receptors in brain membranes of the hamster and gerbil was demonstrated with [³H]CP-96,501. This finding was confirmed by [³H]5-HT binding experiments that also indicated the presence of other 5-HT₁ subtypes (possibly 5-HT_1D, 5-HT_1E) in these species as well as the rat. Negligible specific binding of [³H]CP-96,501 was found in membranes of guinea pig brain, dog hypothalamus, bovine caudate, pig choroid plexus, and several human brain tissues, consistent with the reported absence of the 5-HT_1B receptor subtype in these species. Autoradiographic examination of rat brain sections labeled by [³H]CP-96,501 showed a dense localization in areas known to be enriched in 5-HT_1B receptors (e.g., globus pallidus, substantia nigra, superior colliculus, subiculum). On the other hand, brain sections of dog and guinea pig appeared to show no specific binding of [³H]CP-96,501 by autoradiography, in agreement with the lack of brain 5-HT_1B receptors in these tissues. © 1992 Wiley-Liss, Inc.