Figure 1 A photomicrograph of cerebral cortex sections. (a) The normal structure of this tissue. The nuclei of neurons appear large, vesicular, and with characteristic owl eye appearance. (b) A rat treated with toluene shows many shrunken and dark neurons (arrowhead) as compared with the normal ones, as indicated in the banner at the upper right corner of the figure. Some neurons show karyorrhexis (arrow). (c) A rat treated with toluene and 150 mg citicoline, where damaged neurons are still observed. (d) A rat treated with toluene and 300 mg citicoline shows normal-featured neurons, associated with slightly dilated blood capillaries (hematoxylin and eosin, ×200, ×400).