Sparing of cholinergic neurons following quinolinic acid lesions of the rat striatum.

A combination of immunocytochemical and enzyme histochemical methods have been used to study those neurons which survive lesions of the rat striatum, produced by low doses of the excitotoxin quinolinic acid. Nissl-stained sections revealed that following injection of this toxin many large neurons remained within areas of extensive cell loss. These large cells were found to express both the enzyme acetylcholinesterase and choline acetyltransferase-like immunoreactivity. The surviving cells did not contain the enzyme reduced nicotinamide adenine dinucleotide phosphate or the peptides, somatostatin and neuropeptide Y. This pattern of selective cell sparing was also found following lesions induced by low doses of the toxins ibotenic acid and kainic acid. The survival of large neurons indicates that the excitotoxin-lesioned rat striatum shares common features with the pattern of cell loss found in the caudate-putamen in Huntington's disease. The major difference between these two examples of striatal nerve cell degeneration is, however, the selective preservation of somatostatin/neuropeptide Y/nicotinamide adenine dinucleotide phosphate-diaphorase-containing neurons found in Huntington's disease but not observed following quinolinic acid lesions.