Transport of monoamine and amino acid neurotransmitters by primary astroglial cultures

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Abstract
The transport of [3H]l-glutamate, [3H]l-aspartate, [3H]γ-aminobutyric acid ([3H]GABA), [3H]dopamine, [3H]norepinephrine and [3H]5-hydroxytryptamine (3H-5-HT) was measured in primary astroglial cultures from newborn rat cerebral hemispheres. There was a high-affinity uptake with aK m of 69.0 μM for L-glutamate, 12.3 μM forl-aspartate and 3.1 μM for GABA. The uptake showed properties of high capacity with aV max of 17.0 nmol·mg prot−1·min−1 forl-glutamate, 1.1 nmol·mg prot−1·min−1 forl-aspartate and 0.04 nmol·mg prot−1·min−1 for GABA. No high-affinity high capacity transport system was found for the monoamines studies. Autoradiographic examination demonstrated a heavy deposit of grains suggesting a prominent accumulation of [3H]l-glutamate and [3H]l-aspartate in the astroglial-like cells of the cultures, while the [3H]GABA accumulation was less intense. On the other hand, there was only a weak accumulation of grains after incubating the cultures with [3H]dopamine, [3H]norepinephrine or [3H]5-HT. Thus, astroglial cells in culture accumulate amino acid neurotransmitters and monoamines in different ways with a high-affinity high-capacity uptake of glutamate, aspartate and GABA and a diffusion-uptake of dopamine, norepinephrine and 5-HT.