Application of potassium chloride to the surface of the rat visual cortex differentially affects the expression of...

The purpose of this study was to investigate the effects of topical application of 3 M KCl for 20 minutes to the surface of the rat visual cortex upon the expression of presumptive neuroprotective molecules. Conventional immunohistochemical and immunoblotting techniques revealed a marked reduction of the expression of calbindin and parvalbumin after application of KCl, whereas calretinin, nitric oxide synthase, and the alpha7 subunit of the nicotinic acetylcholine receptor clearly increased following that procedure. Such effects were quantified both in terms of the number of immunoreactive perikarya and optical density of immunoblottings, and were observed as soon as 1 h, and to last at least until 15 days, following KCl application. These results suggest that calbindin and parvalbumin may not be able to exert an appreciable neuroprotective effect in the presence of KCl. On the other hand, calretinin, nitric oxide synthase, and the alpha7-containing nicotinic receptors are possibly upregulated to protect the neurons in which they are expressed.