RT Journal Article
SR Electronic
T1 In Vitro and In Vivo Characterization of Conantokin-R, a Selective Nmda Receptor Antagonist Isolated from the Venom of the Fish-Hunting Snail <em>Conus radiatus</em>
<sup>1</sup>
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 425
OP 432
VO 292
IS 1
A1 H. Steve White
A1 R. Tyler McCabe
A1 Heather Armstrong
A1 Sean D. Donevan
A1 Lourdes J. Cruz
A1 Fe C. Abogadie
A1 Josep Torres
A1 Jean E. Rivier
A1 Ingo Paarmann
A1 Michael Hollmann
A1 Baldomero M. Olivera
YR 2000
UL http://jpet.aspetjournals.org/content/292/1/425.abstract
AB The purification, characterization, and synthesis of conantokin-R (Con-R), an N-methyl-d-aspartate (NMDA) receptor peptide antagonist from the venom of Conus radiatus, are described. With the use of well defined animal seizure models, Con-R was found to possess an anticonvulsant profile superior to that of ifenprodil and dizocilpine (MK-801). With voltage-clamp recording of Xenopus oocytes expressing heteromeric NMDA receptors from cloned NR1 and NR2 subunit RNAs, Con-R exhibited the following order of preference for NR2 subunits: NR2B ≈ NR2A &gt; NR2C ≫ NR2D. Con-R was without effect on oocytes expressing the α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor subunit GluR1 or the kainate receptor subunit GluR6. In mouse cortical neurons voltage-clamped at −60 mV, Con-R application produced a slowly developing block of inward currents evoked by 10 μM NMDA and 1 μM glycine (IC50 = 350 nM). At 3 μM, Con-R did not affect γ-aminobutyric acid- or kainate-evoked currents. Con-R prevented sound-induced tonic extension seizures in the Frings audiogenic seizure-susceptible mice at i.c.v. doses below toxic levels. It was also effective at nontoxic doses in CF#1 mice against tonic extension seizures induced by threshold (15 mA) and maximal (50 mA) stimulation, and it partially blocked clonic seizures induced by s.c. pentylenetetrazol. In contrast, MK-801 and ifenprodil were effective only at doses approaching (audiogenic seizures) or exceeding (electrical and pentylenetetrazol seizures) those required to produce significant behavioral impairment. These results indicate that the subtype selectivity and other properties of Con-R afford a distinct advantage over the noncompetitive NMDA antagonists MK-801 and ifenprodil. Con-R is a useful new pharmacological agent for differentiation between the anticonvulsant and toxic effects of NMDA antagonists. The American Society for Pharmacology and Experimental Therapeutics