Abstract
The sensitivity of various types of recombinant glycine receptors (GlyRs) to ICS-205,930 was studied by fast perfusion in Xenopus laevis oocytes. This compound has previously been shown to potentiate glycine responses in rat spinal neurons between 10 nM and 1 μM, independently of its 5-HT3 antagonist properties. In contrast, submicromolar concentrations of ICS-205,930 failed to affect responses of homomeric GlyRs formed from human α1 or α2 subunits, and micromolar concentrations (1–20 μM) acted differentially on the two types of homomeric receptors, potentiating the responses to glycine (10–20 μM) of α1 homomeric GlyRs and inhibiting the responses of α2 homomeric GlyRs. GlyRs β subunits markedly influenced the modulations induced by ICS-205,930. In oocytes expressing α1/β or α2/β heteromeric GlyRs, low concentrations of ICS-205,930 (20 nM–1 μM) induced a potentiation of glycine responses that was counteracted by an inhibitory effect at higher concentrations. Thus, GlyRs β subunits reduce by 2 orders of magnitude the concentration range potentiating α1-containing GlyRs and are required for potentiation of α2-containing GlyRs. These results reveal a new high-affinity potentiating site on GlyRs, to which β subunits participate. The difference in ICS sensitivity between α1 and α2 GlyRs cannot be explained by their difference in TM2 segment and extracellular domains partly conserved between glycine and 5-HT3 receptors are probably involved in the interaction of some 5-HT3antagonists with GlyRs.
Footnotes
- Received February 24, 2000.
- Accepted June 19, 2000.
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Send reprint requests to: Dr. Dominique Chesnoy-Marchais, Laboratoire de Neurobiologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique UMR-8544, Ecole Normale Supérieure, 46 rue d'Ulm, 75005, Paris, France. E-mail address:chesnoy{at}biologie.ens.fr
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This work was supported by the European Commission (BMH4-CT97-2374) and by l'Association Française contre les Myopathies (MNM97).
- The American Society for Pharmacology and Experimental Therapeutics
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