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Updated: Aug 12, 2026

A Calcium Bioluminescence Assay for Functional Analysis of Mosquito (Aedes aegypti) and Tick (Rhipicephalus microplus) G Protein-coupled Receptors
Published on: April 20, 2011
The spider toxin, argiotoxin636, binds to a Mg2+ site on the N-methyl-D-aspartate receptor complex
1Department of Pharmacology, University of Pittsburgh, PA 15261.
Abstract:
1. The mechanism of action of the arylalkylamine spider toxin, argiotoxin636, on the N-methyl-D-aspartate (NMDA) receptor was investigated by use of [3H]-dizocilpine binding to well-washed membranes obtained from rat brain. 2. Argiotoxin636 decreased [3H]-dizocilpine binding with an apparent potency of about 3 microM. The inhibition of [3H]-dizocilpine by argiotoxin636 was insensitive to the concentration of glutamate, glycine and spermidine in the assay. 3. Argiotoxin636 alone had no effect on the dissociation of [3H]-dizocilpine. However, argiotoxin636 reversed the actions of Mg2+ on the dissociation of [3H]-dizocilpine by decreasing the apparent potency of Mg2+. Argiotoxin636 also reversed the action of Ca2+ on the dissociation of [3H]-dizocilpine. 4. These results suggest that argiotoxin636 exerts a novel inhibitory effect on the NMDA receptor complex by binding to one of the Mg2+ sites located within the NMDA-operated ion channel.
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