Orofacial pain increases mRNA level for galanin in the trigeminal nucleus caudalis of the rat

Abstract The changes of preprogalanin mRNA levels in the superficial dorsal horn neurons (laminae I and II) of the trigeminal nucleus caudalis in response to orofacial pain induced by the injection of 5% formalin into the lips of rats was investigated and compared to those of preproenkephalin A mRNA and preprodynorphin mRNA in the same region by means of in situ hybridization histochemistry. Rapid and marked increases of preprogalanin and preprodynorphin mRNA were observed on the side of the injection, but the increase of preproenkephalin A mRNA level was less pronounced than that of the other two mRNAs, indicating that these peptides have different roles in the dorsal horn analgesic mechanism and that galanin, in addition to opioid peptides, may have a highly specific role in this mechanism.