The transcription factor AP-1 is phorbol ester-regulated and, as such, is considered to be a nuclear target of the signal transduction pathway involving protein kinase C. AP-1 is constituted by the various products of the jun and fos gene family members. These genes belong to the early response class and are inducible in different ways by growth factors, phorbol esters and depolarization. We studied the transcript distribution of c-jun, junB and junD in the rat brain. Our results show that the transcripts for these three genes are differentially distributed in various neuronal tissues. We also provide evidence for developmentally regulated expression of jun genes in post-natal brain. The spatiotemporal pattern of expression of c-jun, junB and junD offers clues to the understanding of the links between gene regulation and neuronal processes.