THE α2-adrenergic agonist clonidine stimulates glutamine uptake and metabolism in primary cultures of mouse astrocytes. This is important because glutamine is a metabolic substrate for these cells. The α2-antagonist yohimbine inhibits the clonidine stimulation, although not completely. The residual effect in the presence of yohimbine can be explained by the fact that this drug is also a serotonin agonist. Idazoxan, which specifically inhibits imidazoline preferring receptors, exerts no inhibition of glutamine uptake. These results suggest that the stimulatory effect of clonidine on glutamine accumulation in mouse astrocytes is due to its effect at an authentic α2-adrenergic receptor site, not at the imidazoline preferring receptor site.