Activity-dependent regulation of tachykinin-like immunoreactivity in neurons of monkey visual cortex.

A monoclonal antibody that recognizes the carboxyl terminus of substance P was used to localize tachykinin-like immunoreactivity in neurons of area 17 of the adult monkey cerebral cortex. Tachykinin immunostaining was examined in normal monkeys, in monkeys receiving monocular injections of the sodium channel blocker TTX for 10 or 15 d, and in monkeys from which the crystalline lens of one eye had been removed 3 or 6 months prior to death. The immunocytochemical staining in each monkey was compared with the histochemical staining for the mitochondrial enzyme cytochrome oxidase (CO). These forms of monocular deprivation produce the most profound changes in the staining of layers II-III and IVC. In layers II-III of normal monkeys, tachykinin-immunoreactive somata are uniformly distributed by immunostained puncta are densely packed in rows of patches that correspond to the rows of CO-stained patches. Following monocular TTX injections, both the patches of CO staining in the deprived-eye columns and the corresponding patches of intense tachykinin immunostaining shrink. Quantitative analyses indicate the numerical density of immunostained somata is reduced by 50% within the deprived-eye rows of patches and is also reduced within regions surrounding the patches in both sets of ocular dominance columns. Following the removal of the lens from one eye, the CO-stained patches and the immunostained patches in one set of rows shrink and the density of immunostained somata in these rows is reduced by 60%. In the alternating rows, the CO staining between patches increases so that many of the patches fuse to form long, continuous bands. Patches of immunostained puncta also enlarge and fuse; the density of immunostained somata in these rows of enlarged patches is approximately 30% greater than normal. In layer IVC of normal monkeys, the CO staining and the tachykinin immunostaining are relatively uniform. Following monocular TTX injections the CO staining and the tachykinin immunostaining are greatly reduced in columns dominated by the injected eye, corresponding to an 80% reduction in the numerical density of immunoreactive somata. By contrast, the CO staining in layer IVC of aphakic monkeys is changed only slightly from normal and the tachykinin immunostaining appears normal. The changes in the density of immunostained somata in both layers II-III and in IVC occur even through the total density of thionin-stained neurons remains normal.(ABSTRACT TRUNCATED AT 400 WORDS)