Abstract
We recently reported the presence of parasympathetic vasodilator fibers in the rat masseter muscle. During the course of studies for neural mechanisms underlying parasympathetic vasodilation evoked by activation of these fibers, we found that cholinergic system would be more involved in the parasympathetic vasodilation in the masseter muscle in females than males. However, it is still questionable whether this is a specific for masseter muscle or not. We explored this question to compare parasympathetic vasodilations in the masseter muscle and lower lip, and increases in blood flow of common carotid artery (CCABF) derived from the orofacial area evoked by the trigeminal-mediated reflex in anesthetized male and female rats. Parasympathetic vasodilations in the masseter muscle and lower lip were much more reduced by atropine in female than male rats. Pretreatment with atropine significantly reduced the CCABF increase in female rats, but not that in male rats. The present study indicates that 1) parasympathetic vasodilations would depend on more cholinergic system in female than male rats, and 2) cholinergic parasympathetic vasodilations accounts for the CCABF increase in female rats. These results suggest that cholinergic system would be more involved in the parasympathetic vasodilation in the orofacial area in females than males. [J Physiol Sci. 2008;58 Suppl:S157]
