However, to date, there are only very few papers reporting any models of inflammatory tongue pain by injecting capsaicin or formalin into the anterior part of the tongue. Moreover, in these studies, only spontaneous pain related behaviors were used to indirectly evaluate the tongue currently pain. In contrast to the extra oral structures, no standard methods are available to directly evaluate behavioral phenotypes of evoked pain hypersensitivity evolving in the tongue. Previously, behavioral and neuronal hyper sensitivity have been observed in some orofacial inflam matory pain models following CFA injection into temporomandibular joint, masseter muscle, or facial skin. Thus, in the present study, we sought for the first time to establish a novel model of inflammatory tongue pain by injecting 5 uL CFA emul sion into the anterior dorsolateral two thirds of the Inhibitors,Modulators,Libraries tongue in adult rats.

Our results show that CFA injection into the tongue elicited clear signs of local tissue inflammation concomi tant with significant reductions in MHWT and HHWT. The results directly indicate the occurrence of mechan ical and heat hypersensitivity in the inflamed tongue in rats. Interestingly, the reduction of HHWT, but not MHWT, recovered on day 15 following CFA Inhibitors,Modulators,Libraries injection, although the existence of thermal hyperalgesia and mechanical allodyniafollowing CFA injection into the upper lip whisker pad continued for a few weeks. It is well known that the transient receptor potential vanil loid 1, activated by noxious heat stim uli, is dominantly expressed in small sized primary afferent neurons and functions to modulate inflamma tion and pain.

Inhibitors,Modulators,Libraries Indeed, CFA induced heat hyper algesia depends on functional changes in TRPV1. On the other hand, one previous retrograde labeling study showed that cell bodies of trigeminal ganglion neurons innervating the lip are significantly smaller in size than those innervating the tongue. Therefore, it is reasonable to speculate that the tongue is innervated by relatively fewer numbers of small sized TRPV1 expressing trigeminal ganglion neurons, which may cause the different time course between MHWT and HHWT measurements following CFA injection into the tongue. Roles of pERK in Vc and C1 C2 neurons in CFA induced behavioral hypersensitivity ERK is a member of the MAPK family that can be phos phorylated after various types of noxious stimuli.

In the trigeminal system, ERK was found to be phos phorylated in many Vc and C1 C2 neurons within 5 min after capsaicin injection into various Inhibitors,Modulators,Libraries orofacial regions, and the number of pERK IR cells increased following increases in the stimulus intensity. These findings strongly suggest Inhibitors,Modulators,Libraries that ERK phosphorylation in Vc and C1 this website C2 neurons is a reliable marker of excitable neurons following noxious stimulation of the orofacial region.