Pharmacological diversity between native human 5-HT1B and 5-HT1D receptors sited on different neurons and involved in different functions

Authors


Dipartimento di Medicina Sperimentale, Sezione di Farmacologia e Tossicologia, Università di Genova, Viale Cembrano 4, 16148 Genova, Italy.

Abstract

  • The releases of [3H]5-hydroxytryptamine ([3H]5-HT) and of endogenous glutamic acid and their modulation through presynaptic h5-HT1B autoreceptors and h5-HT1D heteroreceptors have been investigated in synaptosomal preparations from fresh neocortical samples obtained from patients undergoing neurosurgery.

  • The inhibition by 5-HT of the K+ (15 mM)-evoked overflow of [3H]5-HT was antagonized by the 5-HT1B/5-HT1D receptor ligand GR 127935, which was ineffective on its own; this drug was previously found to behave as a full agonist at the h5-HT1D heteroreceptor regulating glutamate release.

  • The recently proposed selective h5-HT1B receptor ligand SB-224289 also prevented the effect of 5-HT at the autoreceptor, being inactive on its own; in contrast, SB-224289, at 1 μM, was unable to interact with the h5-HT1D heteroreceptor.

  • The inhibitory effect of 5-HT on the K+-evoked overflow of glutamate was antagonized by the h5-HT1D receptor ligand BRL-15572; added in the absence of 5-HT the compound was without effect. BRL-15572 (1 μM) was unable to modify the effect of 5-HT at the autoreceptor regulating [3H]5-HT release.

  • The selective 5-HT1A receptor antagonist (+)-WAY 100135, previously found to be an agonist at the h5-HT1D heteroreceptor regulating glutamate release, could not interact with the h5-HT1B autoreceptor when added at 1 μM.

  • It is concluded that native h5-HT1B and h5-HT1D receptors exhibit a hitherto unexpected pharmacological diversity.

British Journal of Pharmacology (1999) 126, 607–612; doi:10.1038/sj.bjp.0702336

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