Pharmacology of putative glutamate receptors from insect skeletal muscles, insect central nervous system and rat brain.
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, 2.5 mM CaCl2, pH 7.4. The dissociation constants (KDS) ranged from 0.16 to 1.36 microM, and thoracic muscles had 2-4-fold higher density of receptors than brain tissue. The potent inhibitors of housefly brain binding were in decreasing order of effectiveness: L-glutamate greater than L-aspartate = L-cysteate = ibotenate greater than quisqualate greater than L-homocysteate greater than L-APB greater than L-APV greater than NMDA greater than D-APB greater than D-glutamate, with no inhibition by 100 microM of GDEE, dihydrokainate, D-APV, D-homocysteate or D-aspartate. 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. [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. It is suggested that the observed [3H]glutamate binding to insect tissue is not to NMDA or kainate receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D001516:Bees / Q000378:metabolism*; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D003058:Cockroaches / Q000378:metabolism*; D005971:Glutamates / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism; D006793:Houseflies / Q000378:metabolism*; D007700:Kinetics; D009132:Muscles / Q000378:metabolism*; D009420:Nervous System / Q000378:metabolism; D051381:Rats; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D013045:Species Specificity; D013570:Synaptic Membranes / Q000378:metabolism
D005971:Glutamates; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter