title: Kaitocephalin antagonism of glutamate receptors expressed in Xenopus oocytes.
abstract: Kaitocephalin is the first discovered natural toxin with protective properties against excitotoxic-death of cultured neurons induced by N-methyl-d-aspartate (NMDA) or alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainic acid (kainate, KA) receptors. Nevertheless, the effects of kaitocephalin on the function of these receptors were unknown. In this work we report some pharmacological properties of synthetic (-)-kaitocephalin on rat brain glutamate receptors expressed in Xenopus laevis oocytes and, on the homomeric AMPA-type GluR3 and KA-type GluR6 receptors. Kaitocephalin was found to be a more potent antagonist of NMDA receptors (IC(50) = 75 +/- 9 nM) than of AMPA receptors from cerebral cortex (IC(50) = 242 +/- 37 nM) and from homomeric GluR3 subunits (IC(50) = 502 +/- 55 nM). Moreover, kaitocephalin is a weak antagonist of the KA-type receptor GluR6 (IC(50) ~ 100 muM) and of metabotropic (IC(50) > 100 muM) glutamate receptors expressed by rat brain mRNA.
authors.affiliation: Department of Neurobiology and Behavior, University of California at Irvine, Irvine, CA 92697, USA.
authors.forename: Agenor
authors.initials: A
authors.lastname: Limon
authors.forename: Jorge M
authors.initials: JM
authors.lastname: Reyes-Ruiz
authors.forename: Rishi G
authors.initials: RG
authors.lastname: Vaswani
authors.forename: A Richard
authors.initials: AR
authors.lastname: Chamberlin
authors.forename: Ricardo
authors.initials: R
authors.lastname: Miledi