Insulin effect on GABA uptake in astroglial primary cultures

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Abstract
Astroglial cultures from newborn mouse cerebral cortex contain [125I]insulin binding sites. Binding was specific reversible, time dependent and reached equilibrium after 45 min. Insulin analogues compete for this [125I]Insulin binding. Incubation of cerebral cortex astroglial cultures with insulin induced a time-and dose-dependent inhibition of the [3H]GABA high affinity uptake. A decrease in theV max rather than, an effect on theK m was observed. This effect was dose-dependent and effective at 10−10 M. Autoradiographic observations on the cell monolayer showed the presence of two groups of cells: one which strongly takes up [3H]GABA and consist in smaller GFAP positive process-bearing cells and another group of much flatter and larger GFAP positive cells which uptake was lower. The smaller stellate cells were apparently the most sensitive to insulin effect. These results: 1) confirm the presence of insulin binding sites on astroglial primary cultures, 2) show an effect of insulin of [3H]GABA high affinity uptake of these cells; this effect being optimal on a stellate-like population of astrocytes, and 3) indicate, that insulin may interfere in neuromodulation through astroglial signals.