In our work on the interrelationship of neurons and astroglia we have continued to focus on the regulation of C02 fixation. This anaplerotic reaction is localized primarily in astroglial cells with very low activity found in neurons and fibroblasts. The stimulation of C02 fixation by increases in extracellular potassium was found to be specific for glial cells. Mixed cultures of neurons and glia have also been studied. Whereas neurons alone fix very little C02, their presence in mixed cultures markedly alters the distribution of the products of C02 fixation by the astroglial cells. Both the stimulation of C02 fixation in astroglial cells by extracellular potassium and the alteration in the disposition of the products of C02 fixation by the presence of neurons in astroglial cultures are indications of neuronal-astroglial interactions and cooperativity.
