Characterization of sodium-dependent, high-affinity serotonin uptake in rat spinal cord synaptosomes |
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| Authors: | Kenneth A. Stauderman David J. Jones |
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| Affiliation: | 1. Department of Pharmacology, The University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78284 U.S.A.;2. Department of Anesthesiology, The University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78284 U.S.A.;1. Neurobiology Expertise Group, Groningen Institute for Evolutionary Life Sciences (GELIFES), University of Groningen, Groningen, the Netherlands;2. Institute of Synthetic Biology and CEPLAS, University of Düsseldorf, Düsseldorf, Germany;3. Department of Mathematical Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea;4. Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, USA;1. College of Life Sciences, Southwest Forestry University, Kunming 650000, China;2. Key Laboratory of Chemistry of Northwestern Plant Resources, CAS, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China;3. Qingdao Institute for Food and Drug Control, Qingdao 266100, China;4. Yunnan Olive Health Industry Innovation Research and Development CO., Ltd, Lijiang 674100, China;1. The Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA;2. Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA;3. Cell Signaling Technology, Inc, Danvers, Massachusetts, USA;4. La Jolla Institute for Immunology, La Jolla, California, USA;5. Department of Pharmacology, University of California San Diego, La Jolla, California, USA;6. Moores Cancer Center, University of California San Diego, La Jolla, California, USA;7. Department of Chemistry, Yale University, New Haven, Connecticut, USA;1. State Key Laboratory of Heavy Oil Processing, Beijing Key Laboratory of Oil & Gas Pollution Control, China University of Petroleum, Beijing 102249, China;2. Key Laboratory of Microorganism Application and Risk Control of Shenzhen, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China;3. State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China;4. Institute of Nuclear and NewEnergy Technology, Tsinghua University, Beijing 100084, China;5. Environmental Engineering Programs, The Pennsylvania State University, Middletown, PA 17057, USA |
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| Abstract: | Synaptosomal accumulation of [3H]serotonin was used to determine if the rat spinal cord possesses a high-affinity neuronal uptake system for serotonin. Two temperature-dependent accumulation processes were found, one sodium-dependent, the second sodium-independent. Sodium-dependent [3H]serotonin accumulation was linear with sodium concentrations up to 143 mM, was associated with the purified synaptosomal fraction (P2B), and decreased 76% by osmotic lysis, 88% by sonication, and 96% by 0.1% Triton X-100. Drug inhibition studies demonstrated fluoxetine to be the most potent inhibitor of this system (IC50 0.075 microM) while desipramine (IC50 0.43 microM) and nomifensine (IC50 0.95 microM) were less potent. Kinetic analysis revealed that sodium-dependent accumulation in purified synaptosomes was saturable at low [3H]serotonin concentrations (Ku = 50 nM, Vmax = 4 pmol/mg protein/min). Sodium-independent [3H]5-HT accumulation was substantially less sensitive to fluoxetine, desipramine and nomifensine. While sodium-independent accumulation was not significantly affected by osmotic lysis, it was markedly increased by prior sonication of tissue. Also, in contrast to sodium-dependent accumulation, sodium-independent accumulation was evenly distributed in all tissue fractions, and was not saturable at low [3H]serotonin concentrations. It is concluded that sodium-dependent [3H]serotonin accumulation reflects uptake into spinal serotonergic nerve terminals while sodium-independent accumulation probably reflects a temperature-sensitive binding to membrane fragments. Comparison to brain uptake of serotonin and the necessity for using 37 degrees C sodium-free blanks rather than 0 degree C blanks in spinal cord homogenates is discussed. |
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| Keywords: | spinal cord serotonin synaptosomes uptake fluoxetine desipramine nomifensine |
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