The response of the neurolipomastocytoid cells (NLMs) and elements in their vicinity within the central nervous system of various animal species was studied following injection of the animals with the specific mast cell (MC)-discharger compound 48/80. The observed alterations were grouped into those occurring early (0--21 days) and later (up to 18 months). In the present report, only the acute changes are described, light and electron microscopically. Most experimental animals developed prostration, scratching, acral-type reaction, signs of respiratory distress and salivation, and, in the monkey, uncontrollable somnolence. Within about 2 weeks after the injection some animals (especially guinea pigs) manifested various degrees of limb paralysis. The NLMs, like MCs outside the CNS, responded to injection by various degrees of degranulation, vacuolation, marked variation in granule size, apparent cell loss and sometimes an increase in number. Electron microscopically, particulate breakdown products of the granules of the NLMs appeared in the cytoplasm; occasionally there was suggestive evidence that they had passed inward across the vessel wall to reach the lumen, and also outward through the outermost basal lamina. Perivascular astrocytic feet showed swelling and vacuolation shortly after the injection, which was followed by evidence of gliosis and later scarring; occasionally, alterations in the mitochondria were observed. In the spinal cord of the guinea pig, capillary neoformation was observed with endothelial cells and adjacent NLMs taking up tritiated thymidine. The discussion centers on the partial similarity of response to compound 48/80 of the NLMs to that of MCs outside the CNS, and the probable involvement of NLM-damage in the parenchymal changes.
