De novo Expression of Neuropeptides in the Mesencephalic Trigeminal Nucleus of the Rat after Masseteric Nerve Injury

摘要

In normal circumstances, galanin (GAL) and neuropeptide Y (NPY), two putative neuromodulators, are not expressed in the neurons of the mesencephalic trigeminal nucleus (MTN), a unique structure of (pseudo)unipolar sensory neurons in the CNS. Here we demonstrate GAL and NPY immunoreactivity in MTN neurons after an axotomy of n. massetericus in rats. Following survival periods of 7 and 14 days, the MTN neurons on the ipsilateral (axotomized) side display immunostaining, while on the contralateral side they are negative. It can be inferred that axonal injury initiates a cascade of intracellular events, leading to a de novo synthesis of neuroactive substances, such as GAL and NPY, which otherwise are not specific for the MTN neurons under normal conditions. The newly synthesized peptides possibly play a trophic role in the revival process or actively take part in re-establishing the MTN sensory modalities in the orofacial region.