Regional cell count and respiration in the brain of Rana catesbeiana

Cell counts were made in three divisions of the bullfrog brain: (1) olfactory lobestelencephalon, (2) diencephalon-mesencephalon, and (3) the hindbrain; average cellular respiration in potassium-enriched Ringer solution and the rate of respiration in sodium-free medium were tested for their possible relationship to the numbers of glia and numbers of neurons in each region. After restoring some of the sodium ions to sodium-free minces, the percent increase in respiration was plotted for each brain segment and compared to the percent of glia per brain division to determine the glial respiratory contribution. Where glial numbers were greater, the potassium-stimulated respiration was greater; where neuronal numbers were greater, the sodium-free respiration was most prominent. The respiration increased most above the sodium-free rate, when sodium ions were added or when the full amount of sodium was present, in the hindbrain, where the glia appear to metabolize more vigorously and the neurons least actively.