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A low molecular weight toxin isolated from the venom ofthe digger wasp Philanthus triangulum, first noted by T. Piek, is a potent antagonist of transmission at quisqualate-sensitive glutamate synapses of locust leg muscle. This philanthotoxin 433 (PTX-433) has been purified, chemically characterized, and subsequently synthesized along with two closely related analogues. It has a butyryl/tyrosyl/spermine sequence and a molecular weight of 435. Its two analogues, PTX-343 and PTX-334 (the numerals denoting the number of methylenes between the amino groups of the spermine moiety), are also active on the glutamate synapse of the locust leg muscle; PTX-334 was more potent and PTX-343 was less potent than the natural toxin. Such chemicals are useful for studying, labeling, and purifying glutamate receptors and may become models for an additional class oftherapeutic drugs and possibly insecticides. (19). The muscle apodeme was attached to a Grass FT 10-strain gauge with a short strand of Terylene, and the muscle was stretched to maximal body length. The total volume of the bath was about 0.5 ml, and the contents could be replaced within 1 s. The dissection and setting up proceAbbreviation: PTX, philanthotoxin. 4910The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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