[3H]Imipramine Labels Sites on Brain Astroglial Cells Not Related to Serotonin Uptake
- 1 May 1983
- journal article
- research article
- Published by Wiley in Journal of Neurochemistry
- Vol. 41 (5), 1319-1323
- https://doi.org/10.1111/j.1471-4159.1983.tb00827.x
Abstract
Brain astroglial cells, whether from a bulk isolated preparation or in culture, have been shown to take up serotonin actively. [3H]imipramine has been proposed as a specific label for serotonin uptake sites in brain. We therefore studied the binding of [3H]imipramine to C6 astroglial cells in culture to determine if some of the binding of this radioligand in brain homogenates is actually to erotonin transporting sites on glia. [3H]Imipramine binds saturably (Bmax= 202 fmol/mg protein) and with high affinity (KD= 1.72 nM) to C6 cells. This binding is competitively inhibited by other tricyclic antidepressants. The C6 cells actively transport [3H]serotonin with a Km of 2 μ.M and a Vmax of 1080 fmol/106 cells/min. However, the pharmacological profile for inhibition of serotonin uptake does not correlate with the pharmacological profile for inhibition of [3H]imipramine binding. These results suggest that the binding of [3H]imipramine to astroglial cells is not related to their capacity for active uptake of serotonin. Further, in brain homogenates, some of the binding of [3H]imipramine may not be to neuronal uptake sites but rather may be to sites on astroglial cells.Keywords
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