Receptor regulation of the glutamate, GABA and taurine high-affinity uptake into astrocytes in primary culture

Abstract

From experiments using dissociated primary astroglial cultures from newborn rat cerebral cortex, the stimulation of monoamine receptors (α, β and 5HT) was shown to affect the high-affinity uptake kinetics of glutamate, GABA and taurine. In the presence of the α₁ agonist phenylephrine, there was an increased uptake (V_max) of glutamate, while β adrenoceptor activation slightly inhibited the glutamate uptake and stimulated the GABA and taurine uptakes. 5HT₂ receptor stimulation caused a slight inhibition of the taurine uptake. The uptake rate of GABA was not affected by 5HT, α₁ or α₂ receptor agonists and the glutamate uptake was not affected by 5HT or α₂ receptor agonists. Nor was the taurine uptake affected by α₁ or α₂ receptor agonists. The active uptake of aspartate was unaffected by the presence of any of the monoamine receptor agonists used in this study. When the mechanisms behind these effects were studied, the GABA uptake seemed to be mediated via the G protein—adenylate cyclase complex in the receptor domain. Moreover, the K⁺ channels seemed to be involved. The taurine uptake, however, did not seem to be regulated by the same mechanism. It seems more probable that there is a direct interaction between the receptor and carrier of taurine at the membrane level. The mechanism underlying the receptor-regulated glutamate uptake is at present unclear, although it does not seem to involve protein kinase C.