Expression of C-FOS in the Brain Stem of Rats during Hypercapnia

Abstract

Expression of the proto-oncogene c-fos is widely used as a marker of metabolic activation of individual neurones (1,2,12). Expression of this immediate early gene results in the production of the nuclear protein FOS, which forms a heterodimer complex with JUN, the protein product of the immediate early gene c-jun. By acting as a third messenger, the FOS-JUN complex regulates the expression of specific target genes in various types of cells. It is thought that in this way FOS and the products of other early response genes contribute to the genetically determined functional adaptation of the cell to altered stimulus environments (7,15). Various hormones, growth factors and neurotransmitters, as well as depolarisation and voltage gated Ca²⁺ entry into the cell have been shown to induce a rapid but transitional transcription of the c-fos gene in various types of neurones (6,8). Once FOS is produced in sufficient amounts depending on the duration and intensity of the activating stimulus, a FOS-like immunoreactivity (FOS-LI) can be demonstrated in the nuclei of these cells.