Differences in the autonomic regulation of temperature in the lower lip and tongue during activation of the lingual nerve.

Orofacial temperature influences orofacial functions and is related to hemodynamics mediated by the autonomic nerves. Although the properties of autonomic vasomotor responses differ in orofacial tissues, differences in the autonomic regulation of orofacial temperature are unclear. We examined the differences in blood flow (BF) and temperature (Tm) between the extraoral (lower lip) and intraoral tissues (tongue) of urethane-anesthetized rats. Noncholinergic parasympathetic vasodilation evoked by trigeminal-mediated reflex elicited significant increases in BF and Tm in both tissues, and these increases were larger in the tongue than in the lower lip. Activation of cervical sympathetic nerves significantly decreased BF and Tm in both tissues. These decreases were restored by parasympathetic reflex vasodilation; the effects were larger in the tongue than in the lower lip. Our results suggest that parasympathetic vasodilation is involved in the maintenance of BF and Tm, and that the effects may be greater in intraoral than in extraoral tissues.