Differential expression of immediate-early genes, c-fos and zif268, in thevisual cortex of young rats: Effects of a noradrenergic neurotoxin on their expression

We investigated the expression pattern of two immediate-early genes, zif268 and c-fos, under various visual conditions using immunohistochemical and n orthern blot analysis in the visual cortex of young rats. The basal express ion of c-fos was low and was further reduced by dark; rearing that lasted f or one week. A marked and transient increase was induced upon visual stimul ation applied immediately after dark rearing. Zif268 showed a relatively hi gh basal level. Its expression was reduced by dark rearing of the animals, but returned rapidly to the basal expression level following the introducti on of light. Administration of N-(2-chloroethyl) -N-ethyl-2-bromobenzylamin e, a selective noradrenergic neurotoxin, suppressed the basal expression of c-fos messenger RNA. The response of c-fos to photo-stimulation was also s ignificantly lower in the visual cortex of N-(2-chloroethyl)-N-ethyl-2-brom obenzylamine-treated young rats. In contrast, no significant change in zif2 68 expression was detected between normal and N-(2-chloroethyl)-N-ethyl-2-b romobenzylamine-treated animals. These findings suggest that differential expression of these immediate-earl y genes is involved in the activity-dependent regulation of cortical functi on. One possibility is that the noradrenergic system controls cortical func tion, including plasticity, by modifying the expression of c-fos. (C) 1999 IBRO. Published by Elsevier Science Ltd.