ABSENCE OF PARASYMPATHETIC VASODILATATION IN CAT DENTAL-PULP

The existence and nature of parasympathetic nerve fibers in the dental pulp have long been a subject for discussion; indeed, vasodilator res ponses mediated by such nerve fibers have yet to be conclusively demon strated in the dental pulp. This study was designed to determine wheth er parasympathetic vasodilator mechanisms do or do not exist in the ca t dental pulp. Dynamic changes in pulpal blood flow (PBF), with mandib ular lip blood flow (LBF) recorded as a control, were investigated in cat mandibular canine teeth by means of laser Doppler velocimetry. Per ipheral trigeminal afferents (see below) were stimulated electrically to confirm that somato-parasympathetic reflex vasodilatation could be induced. The peripheral cut ends of the facial and glossopharyngeal ne rve roots, which have been reported to contain parasympathetic nerve f ibers to the oral tissues, were then stimulated intracranially. Electr ical stimulation of trigeminal afferents (in the infraorbital nerve or the maxillary buccal gingiva) caused no change in PBF but did increas e ipsilateral LBF. Neither facial nor glossopharyngeal nerve root stim ulation caused a PBF increase, though both elicited increases in ipsil ateral LBF. The vasodilator responses in the lip were sensitive to gan glion blockade (with hexamethonium), indicating vasodilatation via act ivation of parasympathetic vasodilator fibers. In contrast, intracrani al stimulation of the trigeminal nerve root induced increases in both PBF and LBF which were reduced by pre-treatment with tripelennamine, i ndicating antidromic vasodilatation via the trigeminal sensory nerve. These results suggest that a parasympathetic vasodilator mechanism is not present in feline dental pulp.