[Implication of the neuropeptides methionine enkephalin, neurotensin and somatostatin of the caudal trigeminal nucleus in the experimental migraine].

Introduction. Primary peptidergic sensory neurons of the trigeminal ganglion that innervate the cerebral dura have been involved in the pathogenesis of headache, including the migraine. In addition, it is known that nociceptive central processes of the trigeminal neurons terminate in the caudaltrigeminal nucleus. Moreover, the electrical stimulation ofthe trigeminal ganglion has been used as an experimental model in order to study the vascular headache, including the migraine. Aim. To study whether there is or not a decrease of the immunoreactivity for methionine-enkephalin, somatostatin and neurotensin in the caudal trigeminal nucleus after electrical stimulation of the trigeminal ganglion. Material and methods. The trigeminal ganglia of Wistar albino rats of both sexes were electrically stimulated (frequency, 5 Hz; duration, 5ms; intensity, 0,8-1.4 mA) and unilaterally for five minutes. Sections of the medulla oblongata containing the caudal trigeminal nucleus were obtained and processed for immunocylochemistry, in which specific antibodies were used against methionine-enkephalin, neurotensin andsomatostatin-28. Results. In stimulated animals, we observed a decrease in the immunoreactivityfor the three neuropeptides studied in the stimulated (ipsilateral) side, in comparison with the not stimulated side (contralateral). In control animals (not stimulated) the degree of the immunoreactivity was the same on both sides. Conclusions. 1. The decrease of the immunoreactivity in the ipsilateral side (stimulated) suggests that methionine-enkephalin, neurotensin and somatostatin-28 are released in the caudal trigeminal nucleus after electrical stimulation of the trigeminal ganglion; 2. Methionine-enkephalin and somatostatin-28 could act in the caudal trigeminal nucleus as inhibitors (with antinociceptive action) of another released exciters neuropeptides (with nociceptive action); and 3. These data will allow in the future to try new therapeutic strategies (e.g., the inhibition of the receptors implicated...), in order to alleviate certain headaches.