Astroglial cells are able to transport various neurotransmitters and neuromodulators; the pattern and heterogeneity of neurotransmitter transporters expressed by astrocytes is dependent on the neurones they are associated with. Astrocytes can express transporters for monoamines (dopamine, norepinephrine and serotonin), yet the actual contribution of these uptake pathways in the regulation of brain monoamine levels remains undetermined. Astrocytes are reported to have a relatively high capacity for histamine uptake. In addition, certain astroglial cells express a Na+/Cl- dependent taurine transporting system, which is able to function in both forward (taurine uptake) and reverse (taurine release) modes. The reversal of the transporter requires cell depolarization (up to -50 mV) together with an increase in the intracellular Na+ concentration above 40 mM; these conditions most likely may occur only during severe ischaemia. Functionally the taurine transporter (working in the forward mode) could be involved in taurine redistribution following a hypo-osmotic shock.
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