Binding of Dihydroergosine to 5-HT_1A Receptors of Human and Rat Brain

Sa？etak Interaction of the ergot alkaloid dihydroergosine with the binding of (3H)8-hydroxy-2-(di-n-propylamino)tetralin (3H8-OH-DPAT), a selective agonist for 5-HT1A binding sites, to hippocampal membra-nes isolated from human and rat brain was studied. Competition binding experiments showed that dihydroergosine is a potent dis-placer of (3H)8-OH-DPAT binding at brain 5-HT1A receptors of both species. Scatchard analysis of (3H)8-OH-DPAT binding to rat hippocampal membranes in the presence of dihydroergosine revealed that this ergot compound markedly decreases the number and the affinity of hippocampal (3H)8-OH-DPAT labelled binding sites. Pre-incubation of rat hippocampal membranes for 180 min with dihy-droergosine (2 nmol dm-3) completely prevented the binding of (3H)8-OH-DPAT (2 nmol dm-3). The data suggest that dihydroergo-sine is approximately as potent a ligand as 8-OH-DPAT for the hippocampal 5-HT1A receptors from human and rat brains, although their kinetics of association and dissociation are apparently different