The stimulatory effect of L-glutamate and related agents on inositol 1,4,5-trisphosphate production in the cestode Hymenolepis diminuta |
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| Affiliation: | 1. National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), Shanghai 201306, China;2. Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources (Shanghai Ocean University), Ministry of Education, Shanghai 201306, China;3. International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology, Shanghai 201306, China;1. National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, China;2. Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China;3. International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology, China;1. National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, China;2. Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University, Shanghai 201306, China;3. International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology, China |
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| Abstract: | The effects of L-glutamate, acetylcholine, and serotonin (5HT) were examined on generation of inositol 1,4,5-triphosphate [Ins(1,4,5)P3], in membrane preparations of the cestode Hymenolepis diminuta. Only L-glutamate and acetylcholine stimulated a significant elevation in Ins(1,4,5)P3. The response to L-glutamate was stereospecific; D-glutamate or L-aspartate were not as potent.A role for G-protein(s) was supported by the observations that sodium fluoride stimulated Ins(1,4,5)P3 generation, and the L-glutamate response was potentiated by GTP and GTP-S and was suppressed by GDPS. However, studies with pertussis and cholera toxins indicated that the putative G-protein(s) was not pertussis or cholera toxin sensitive.The pharmacological profile of the L-glutamate response was examined partially. Trans-ACPD was a very effective agonist at 10−5M. While 10−3M L-glutamate, NMDA, and AMPA significantly elevated Ins(1,4,5)P3 levels, quisqualate and kainate did not. The elevation of Ins(1,4,5)P3 levels by L-glutamate and NMDA was antagonized by the specific glutamatergic antagonists AP-5, AP-7, CNQX, and CPP. While the response to ACPD was antagonized by AP5, CPP and CPG, CNQX was without effect.Collectively, the data support the hypothesis that in the cestode H. diminuta, L-glutamate activation of a metabotropic (ACPD) and/or ionotropic-like AMPA/NMDA receptor subtypes proceeds via a G protein(s) to enhance phospholipase C activity, ultimately resulting in the elevation of Ins(1,4,5)P3 levels in the tissues. |
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