Central distribution of A delta and C afferent fibres from the dental pulp and periodontium in the rat

Non c'è abstract Di seguito allego l'introduzione Several electrophysiological findings show that jaw muscle activity is influenced by pain signals arising from orofacial tissues (Svensson et al., 2000). There is no doubt that during the stimulation of oral nociceptors the jaw-closing muscles are inhibited and the digastric muscle is excited (Pertovaara et al., 2000). However, the functional linkage between nociceptive inputs, carried by A delta and C afferent fibres, and oral reflexes needs to be demonstrated. Since the proprioceptive neurons of the mesencephalic trigeminal nucleus (MTN) are considered an important relay in the circuits underlying oral reflexes (Lazarov, 2000), we have considered the proprioceptive pathway as a possible site of central termination of the nociceptive trigeminal ganglion cells supplying dental pulp and periodontium. Therefore, after capsaicin treatment to induce the selective degeneration of the nociceptive afferents (Jancso and Lawson, 1990), we have investigated the presence of degenerating synapses on the soma of the trigeminal mesencephalic neurons and on their terminals (axo-assonic synapses) on the trigeminal motor nucleus (Vmot) (Bae et al., 1996).