Expression of the bZIP transcription factor c-Fos in the nucleus tractus solitarius (NTS) of the brain stem may allow for genomic encoding of an unconditioned stimulus (US) during taste aversion learning. Dimerization of c-Fos with other bZIP proteins of the Jun family is necessary to enable transcriptional efficacy at the AP-1 sequence of putative target gene promoter regions. The present study examined the regulation of Fos and Jun proteins by LiCl. Double immunofluorescence labelling revealed that LiCl causes a coordinate upregulation of c-Fos, FosB and JunB, and these proteins are colocalized in a majority of cells examined in NTS, parabrachial nucleus (PBN), and central nucleus of the amygdala (CeA). This study demonstrates that a coordinate signalling response occurs in relevant brain regions in response to LiCl.