Inhibition of [3H]CGP 39653 binding to NMDA receptors by a P2 antagonist, suramin

Abstract

Suramin, which has been used for more than 50 years as an anthelmintic in humans, has recently been shown to inhibit P2 purinoceptors in the CNS and to block glutamate-evoked excitatory potentials in hippocampus. We now report that suramin inhibits (IC50 ~ 100 µM) the binding of [3H]CGP 39653, a ligand specific for NMDA-type glutamate receptors in brain. Consequently, suramin at concentrations used sometimes in physiological experiments may act as both P2x and NMDA antagonist. Since both NMDA receptors and P2x-subtype of purinoceptors form Ca2+-selective channels, suramin may block Ca2+ entry into neurones depolarized by either ATP, l-glutamate or any other neurotransmitter or drug acting via P2x or NMDA receptors.