Experimental tooth movement upregulates preproenkephalin mRNA in the rat trigeminal nucleus caudalis and oralis

Levels of preproenkephalin mRNA expression in trigeminal subnucleus complex by noxious tooth movement stimuli were examined using in situ hybridization. At 24 h, preproenkephalin mRNA expression was significantly upregulated in the ipsilateral trigeminal subnucleus caudalis (P < 0.05), and in the subnucleus oralis (P < 0.05). These findings suggested that enkephalinergic inhibitory systems could be activated during tooth movement, and that subnucleus oralis may be involved in modulation of the nociception, as well as the subnucleus caudalis.