[3H]Spiroxatrine labels a serotonin/sub 1A/-like site in the rat hippocampus

[3H]Spiroxatrine was examined as a potential ligand for the labeling of 5-HT/sub 1A/ sites in the rat hippocampus. Analysis o the binding of [3H]spiroxatrine in the absence and presence of varying concentrations of three monoamine neurotransmitters revealed that serotonin (5-HT) had high affinity for the [3H]spiroxatrine binding sites, consistent with the labeling of 5-HT1 sites, while dopamine and norepinephrine had very low affinity. Saturation studies of the binding of [3H]spiroxatrine revealed a single population of sites with a K/sub d/ = 2.21 nM. Further pharmacologic characterization with the 5-HT/sub 1A/ ligands 8-hydroxy-2-(di-ni-propylamino)tetralin, ipsapirone, and WB4101 and the butyrophenone compounds spiperone and haloperidol gave results that were consistent with [3H]spiroxatrine labeling 5-HT/sub 1A/ sites. This ligand produced stable, reproducible binding with a good ratio of specific to nonspecific binding. The binding of [3H]spiroxatrine was sensitive to GTP, suggesting that this ligand may act as an agonist. 21 references, 5 figures, 2 tables