Jun B, c-jun, jun D and c-fos mRNAs in nucleus caudalis neurons: rapid selective enhancement by afferent stimulation

In situ hybridization using cDNAs complementary to specific regions of the mRNAs encoding 3 members of the jun transcription factor gene family and c-fos reveals modest levels of hybridization over superficial laminae of the nucleus caudalis of the spinal tract of the trigeminal in sections taken from unstimulated brains. Jun B expression is markedly and rapidly enhanced ipsilateral to electrical stimulation of the trigeminal ganglion. C-fos mRNA levels also show changes, especially after higher intensity stimulation. Smaller alterations in c-jun (jun A) and jun D do not reach statistical significance. In each instance of altered expression, more neurons express hybridization densities above background levels after stimulation. Parallels between these alterations and changes in the expression of preproenkephalin in these same neuronal populations are discussed.