The effect of tooth clenching on the sensory and pain perception in the oro-facial region of symptom-free men and women

The aim of this study was (i) to examine the effect of light tooth contact as in diurnal tooth clenching on the tactile detection threshold (TDT), the filament-prick pain detection threshold (FPT) and the pressure pain threshold (PPT) in the oro-facial region and (ii) to examine the possible gender difference in this effect on the tactile and pain perception. Twenty healthy volunteers participated. The TDT and the FPT were measured by means of Semmes-Weinstein monofilaments, on the cheek skin (CS) overlying the masseter muscles (MM) and on the skin overlying the palm side of the thenar skin (TS). The PPT was measured at the central part of the MM using a pressure algometer. Each parameter was measured before and after keeping light tooth contact for 5 min (session 1) and after keeping the jaw relaxed for 5 min (session 2) as a control. Although there were no significant session effects on any of the parameters, there were significant effects of experimental condition on the TDT in both men and women (P < 0·001). Men had a significant higher FPT of the left CS (P < 0·05) and TS (P < 0·01) and a significant higher PPT of the MM than women (P < 0·001). These results illustrate that sensitivity to pain (FPT, PPT) was higher in women than in men. Although there were no significant gender differences in habituation of sensory perception, the increase of TDT after clenching/no clenching was larger in women, which warrants further study

Effects of midazolam on acquisition and extinction of conditioned taste aversion memory in rats.

Some intravenous anesthetic agents such as midazolam are known to induce anterograde and retrograde amnesia. We analyzed the effect of midazolam by the conditioned taste aversion (CTA) acquisition and retention. After the rats were offered 0.1% sodium saccharin (Sac) as conditioned stimulus (CS), an intraperitoneal (i.p.) injection of several concentrations (5-30mg/kg) of midazolam was followed by an i.p. injection of 0.15M LiCl (2% of body weight) as unconditioned stimulus (US). The rats, which acquired CTA by every CS-US paradigm, strongly avoided Sac on the 1st test day after conditioning and maintained the avoidance for 3 days. We have already reported that Sac intake abruptly increased on the 2nd test day and the almost complete extinction occurred on the 3rd test day after conditioning by injection of subhypnotic dose of propofol before LiCl-injection. In contrast, we found that subhypnotic dose of midazolam suppressed not only CTA acquisition, but also CTA retention. On the other hand, an alpha2-adrenergic blocker, yohimbin (1mg/kg) suppressed only the CTA retention. These results suggest that the subhypnotic doses of midazolam firstly affect the acquisition mechanism of the CTA memory (CTAM), resulting the suppression of the retention of CTAM

Effects of midazolam on acquisition and extinction of conditioned taste aversion memory in rats.

Some intravenous anesthetic agents such as midazolam are known to induce anterograde and retrograde amnesia. We analyzed the effect of midazolam by the conditioned taste aversion (CTA) acquisition and retention. After the rats were offered 0.1% sodium saccharin (Sac) as conditioned stimulus (CS), an intraperitoneal (i.p.) injection of several concentrations (5-30mg/kg) of midazolam was followed by an i.p. injection of 0.15M LiCl (2% of body weight) as unconditioned stimulus (US). The rats, which acquired CTA by every CS-US paradigm, strongly avoided Sac on the 1st test day after conditioning and maintained the avoidance for 3 days. We have already reported that Sac intake abruptly increased on the 2nd test day and the almost complete extinction occurred on the 3rd test day after conditioning by injection of subhypnotic dose of propofol before LiCl-injection. In contrast, we found that subhypnotic dose of midazolam suppressed not only CTA acquisition, but also CTA retention. On the other hand, an alpha2-adrenergic blocker, yohimbin (1mg/kg) suppressed only the CTA retention. These results suggest that the subhypnotic doses of midazolam firstly affect the acquisition mechanism of the CTA memory (CTAM), resulting the suppression of the retention of CTAM

Influence of soft diet feeding on development of masticatory function

Stomatognathic function is developed in steps from the latter half of infancy up to childhood. This period is thought to be critical for stomatognathic function acquisition. In this study, we investigated how the consistency of the daily diet after weaning affects the development of stomatognathic function in mice. C3H mice were divided into liquid- and solid-diet group. Three-dimensional jaw-movement tracking and jaw-muscle electromyography (EMG) were recorded simultaneously during chewing of pellet and bread at 11 weeks of age. As a result, we found that (1) The masseter activity was larger in the liquid-diet group than the solid-diet group. (2) Total cycle duration indicating chewing rhythm and gape size indicating burst pattern were significantly longer and larger during pellet chewing than bread chewing in the solid-diet group. On the other hand, there was no significant difference in both parameters in the liquid-diet group. These results suggest that greater EMG bursts are necessary, since the masticatory muscles are weaker in mice fed with liquid diet, and that the capacity to perceive the consistency of diet is reduced in these mice. The development of the mechanism to regulate chewing rhythm and pattern is considered to be impeded when raised on soft diet

Measurement of protease activity of exfoliative toxin A using synthetic peptidyl substrates and correlation between in vivo and in vitro activities

Exfoliative toxin A (ETA) produced by Staphylococcus aureus causes bullous impetigo and staphylococcal scalded skin syndrome. The exfoliative activity of ETA is ascribed to its highly restricted degradation between Glu381-Gly382 of desmoglein 1, a component protein of desmosomes. Since the peptidase activity of ETA has been yet to be demonstrated other than desmoglein 1, the entity as a peptidase and its molecular mechanism remain to be elucidated. In the present study, we determined the peptidase activity using recombinant ETA molecules and synthetic fluorescent peptidyl substrates, while the exfoliative activity was examined by a neonatal mouse model. Although peptidase activity was trivial as compared with the S. aureus glutamyl endopeptidase GluV8, pro-ETA starting from Phe24 (Phe24-ETA) and the mature form from Glu39 (Glu39-ETA) exhibited the activities toward LLE-, AE-, and LE-MCA, but not toward LLQ-, LD- or AAA-MCA, indicating a Glu-specific endopeptidase activity. This activity was statistically higher in Glu39-ETA than Phe24-ETA and was inhibited by the serine protease inhibitor Pefabloc. Deletion of the α1 region at positions 42-56 as well as substitution of active Ser233 to Ala abrogated the peptidase activity. In accord with these results, intraepidermal blister formation and epidermolysis were induced more exclusively by Glu39-ETA than Phe24-ETA. ETAs without proteolytic activity as well as GluV8 did not cause an exfoliative reaction. These results suggest that the highly restricted Glu-specific endopeptidase activity of ETA is involved in exfoliative activity and that the α1 region is required for these functions