Expression of neuropeptides in the rat mesencephalic trigeminal nucleus after peripheral axotomy

Certain populations of dorsal root ganglion cells upregulate galanin (GAL) and neuropeptide Y (NPY) after peripheral axotomy. Less is known of the functional properties of the neurones reacting in this way. The primary sensory mesencephalic trigeminal (Me5) neurones are considered to have purely proprioceptive functions. In this study immunohistochemistry and in situ hybridization have been used to investigate the expression of NPY and GAL in Me5 neurones after peripheral axotomy. Both methods revealed a transient upregulation of GAL and NPY in Me5 neurones which was first observed 3 days postoperatively, peaking at 1 and 2 weeks and then being reduced. The results show that proprioceptive neurones may upregulate these peptides as a consequence of injury.