Pharmacology of putative glutamate receptors from insect skeletal muscles, insect central nervous system and rat brain

Shebl M. Sherby, Mohyee E. Eldefrawi, Keith A. Wafford, David B. Sattelle, Amira T. Eldefrawi

    Research output: Contribution to journalArticlepeer-review

    Abstract

    1. Binding of [3H]glutamate to housefly brain and honeybee brain and thoracic muscle membranes as well as to the American cockroach nerve cord was measured in Na+-free Tris-citrate buffer, 2.5mM CaCl2, pH 7.4. The dissociation constants (KDs) ranged from 0.16 to 1.36 μM, and thoracic muscles had 2-4-fold higher density of receptors than brain tissue. 2. The potent inhibitors of housefly brain binding were in decreasing order of effectiveness: l-glutamate > l-aspartate = l-cysteate = ibotenate > quisqualate >l-homocysteate > l-apb > l-apv > NMDA > d-apb > D-glutamate, with no inhibition by 100 μM of GDEE, dihydrokainate, d-apv, d-homocysteate or d-aspartate. 3. The drug specificity of [3H]glutamate binding sites in housefly brain was generally similar to that of binding sites in housefly muscle, except that the former had a slightly higher affinity for l-APB, l-homocysteate and NMDA. 4. [3H]Glutamate binding to insect tissues differed in its drug sensitivity from binding to rat brain. Binding to insect membranes was much less sensitive to l-APB, d-APB, APV, homocysteate, l-cysteate, quisqualate and ibotenate. However, the insect binding site was much more stereoselective for the l than d isomers of glutamate and aspartate, while the rat brain site was more stereoselective for APB. 5. It is suggested that the observed [3H]glutamate binding to insect tissue is not to NMDA or kainate receptors. A majority of binding is possibly to a depolarizing-type receptor with a relatively low affinity for quisqualate and a higher affinity for l-aspartate; while some of the binding is Cl--dependent with low affinity for APB and may represent transport into resealed membranes or binding to a hyperpolarizing glutamate receptor. © 1987.
    Original languageEnglish
    Pages (from-to)99-106
    Number of pages7
    JournalComparative Biochemistry and Physiology. Part C: Comparative Pharmacology
    Volume87
    Issue number1
    Publication statusPublished - 1987

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