Aspirin (acetylsalicylic acid, ASA) treatment resulted in a significant decrease in the amount of the sulfur-rich Gomori-positive material present in the cytoplasm of periventricular glia. It also caused the accumulation of the Gomori-positive neurosecretory material in the supraoptic and paraventricular nuclei and, most pronounced, in the neurosecretory axons of the paraventricular- and supraoptic-neurophypophysial tract.