Neuron and glia in culture produce varied trophic factors including extracellular matrix, growth factor cell adhesion factor, and cell growth inhibitory factor, and further secrete them into the culture medium. These factors are classified into two kinds of factors in the view-point of mechanism of action, an autocrine factor with the self-production and -stimulation, and a paracrine factor with the adjacent cell stimulation through the extracellular space but not via the blood stream. In the central nervous system, these trophic factors produced by both neuron and glia are thought to regulate the cell growth and differentiation of those cells by autocrine or paracrine system, and support the function of the central nervous system.