In Vitro Effects of Arachidonic and L-Glutamic Acids on the High-Affinity Choline Transport in Rat Hippocampus |
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Authors: | Kri?tofiková Zdena Klaschka Jan |
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Institution: | (1) Prague Psychiatric Centre, Ústavní 91, 181 03 Prague, Czech Republic |
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Abstract: | A second messenger role for arachidonic acid (AA) in the regulation of the high-affinity choline uptake (HACU) was suggested. It was repotted that micromolar concentrations of AA applied in vitro decreased the HACU values and increased the specific binding of 3H]hemicholinium-3 (3H]HCh-3). It was published that L-glutamic acid (GA) applied in vivo produced a fall in the HACU values. In addition, GA liberates free AA. In this study, an ability of GA to influence in vitro the activity of presynaptic cholinergic nerve terminals via its effect on the release of AA is investigated in hippocampal synaptosomes of young Wistar rats. Millimolar concentrations of GA decrease both the high- and low-affinity choline uptake, the specific as well as nonspecific binding of 3H]HCh-3 and the activity of Na+,K+-ATPase. Kinetic analysis (Lineweaver-Burk and Scatchard plots) reveals a change in Vmax and Bmax, but not in KM and KD. It appears very likely that under normal conditions GA applied in vitro is not able to change markedly the choline transport via its effect on the release of AA. Results confirm the hypothesis about an indirect inhibitory role for glutamatergic receptors on cholinergic cells. |
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Keywords: | High-affinity choline uptake hemicholinium-3 arachidonic acid L-glutamic acid presynaptic nerve terminals |
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