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Journal of Experimental Biology 60,783-794 (1974)
Published by Company of Biologists 1974

L-Glutamate in Arthropod Blood Plasma: Physiological Implications

LARRY L. MURDOCK ¹ and GRACE Y. CHAPMAN ¹

¹ Fachbereich Biologie, Universität Konstanz, D 775 Konstanz, Postfach 733

1. The L-glutamate concentration in blood plasma of the crayfish, Astacus leptodactylus and A. astacus, was found to be about 1.5x10^-6 M, as measured by a specific enzymatic method. Even 10 times this concentration of L-glutamate in saline failed to significantly affect neuromuscular transmission in the dactyl abductor muscle, although higher concentrations caused depression.

2. L-Glutamate in the blood plasma of the spider, Dugesiella hentzii, amounted to 7x10^-6 M. As in the crayfish, even 10 times this concentration of L-glutamate in saline failed to affect neuromuscular transmission in the promoter tibiae muscle, while higher concentrations caused depression.

3. The concentration of L-glutamate in Locusta mgratoria blood plasma, ca. 7x10^-5 M, would appear to be sufficient to cause depression of neuromuscular transmission in vivo. Perfusion of the extensor tibiae preparation with 15x10^-5 M L-glutamate caused marked depolarization and decreases in the size of e.j.p.s.

4. It appears that in the tarantula and the crayfish, blood plasma L-glutamate does not pose difficulties for neuromuscular transmission. In the locust, additional protective mechanisms which are not able to function in the saline-perfused in vitro preparation must be at work in the living animal.