Effect of local administration of eicosapentaenoic acid on the jaw-opening reflex in rats.

Although eicosapentaenoic acid (EPA) application in vitro inhibits voltage-gated Na+ (Nav) channels in excitable tissues, the acute local effect of EPA on the jaw-opening reflex in vivo remains unknown. The aim of the present study was to determine whether local administration of EPA to adult male Wistar rats could attenuate the excitability of the jaw-opening reflex in vivo, including nociception. The jaw-opening reflex evoked by electrical stimulation of the tongue was recorded by a digastric muscle electromyogram (dEMG) in pentobarbital-anesthetized rats. The amplitude of the dEMG response was significantly increased in proportion to the electrical stimulation intensity (1×-5× threshold). At 3×, local administration of EPA dose-dependently inhibited the dEMG response, lasting 60 min, with maximum inhibition observed within approximately 10 min. The mean magnitude of dEMG signal inhibition by EPA was almost equal to that observed with a local anesthetic, 1% lidocaine, and with a half dose of lidocaine plus a half dose of EPA. These findings suggest that EPA attenuates the jaw-opening reflex, possibly by blocking Nav channels of primary nerve terminals, and strongly support the idea that EPA is a potential therapeutic agent and complementary alternative medicine for the prevention of acute trigeminal nociception.

Age Differences in Naloxone Reversibility of Electroacupuncture on the Jaw Opening Reflex in Rats.

Background: Electroacupuncture is one of the most popular physical treatments for clinical pain, but the potential influence of a patient's age on the effectiveness of electroacupuncture treatment has not been clearly established. Objectives: The present study aimed to detect a potential difference in electroacupuncture- induced analgesia between juvenile and adult rats. Methods: In this study, we investigated the effects of electroacupuncture treatment on the nociceptive jaw-opening reflex evoked by tooth-pulp stimulation in juvenile and adult rats. Results: Our results showed there were age differences in electroacupuncture-induced analgesic effects in rats, especially with naloxone antagonization. The ratio of naloxonereversibility against electroacupuncture analgesia was greater in adult rats than in juvenile rats. Conclusion: These results suggest that electroacupuncture analgesia is produced mainly by the non-opioid system in juvenile rats and by the opioid system in adult rats.

The last Palaeoproteus (Urodela: Batrachosauroididae) of Europe.

The Batrachosauroididae are an enigmatic group of salamanders known from the Cretaceous and Tertiary of North America and Europe. In Europe, the family is known only by two species of the genus Palaeoproteus. The genus has limited distribution in Western and Central Europe. In the present paper, we describe a new species, Palaeoproteus miocenicus, from the early late Miocene (11-9 Ma) of Austria and Ukraine, representing the youngest record of the family Batrachosauroididae from the Neogene of Europe. The new species differs from the Paleogene representatives of the genus by 12 characters, including large body size, the long anterior extension of the Meckelian groove and the size and shape of the odontoid process on the dentary. The µCT scanning of bones of the new species revealed novel features (e.g. anterior extension of Meckelian groove, interconnected network of canals and small cavities in atlas) observable only in this species. P. miocenicus inhabited aquatic environments, which existed under wet climatic conditions with mean annual precipitation higher than 900 mm. The new species expands the temporal range of the genus by at least 30 million years and enlarges the palaeogeographic distribution of the genus into Eastern Europe.

Amiskwia is a large Cambrian gnathiferan with complex gnathostomulid-like jaws.

Phylogenomic studies have greatly improved our understanding of the animal tree of life but the relationships of many clades remain ambiguous. Here we show that the rare soft-bodied animal Amiskwia from the Cambrian of Canada and China, which has variously been considered a chaetognath, a nemertine, allied to molluscs, or a problematica, is related to gnathiferans. New specimens from the Burgess Shale (British Columbia, Canada) preserve a complex pharyngeal jaw apparatus composed of a pair of elements with teeth most similar to gnathostomulids. Amiskwia demonstrates that primitive spiralians were large and unsegmented, had a coelom, and were probably active nekto-benthic scavengers or predators. Secondary simplification and miniaturisation events likely occurred in response to shifting ecologies and adaptations to specialised planktonic habitats.

Local anesthetic effect of docosahexaenoic acid on the nociceptive jaw-opening reflex in rats.

Although docosahexaenoic acid (DHA) administration suppresses sodium channels in primary afferent sensory neurons, the acute local effect of DHA on the trigeminal nociceptive reflex remains to be elucidated, in vivo. Therefore, the aim of the present study was to investigate whether local administration of DHA attenuates the nociceptive jaw-opening reflex (JOR) in vivo in the rat. The JOR evoked by electrical stimulation of the tongue was recorded by a digastric muscle electromyogram (dEMG) in pentobarbital-anesthetized rats. The amplitude of the dEMG response was significantly increased in proportion to the electrical stimulation intensity (1-5 x threshold). At 3 x threshold, local administration of DHA (0.1, 10 and 25 mM) dose-dependently inhibited the dEMG response, and lasted 40 min. Maximum inhibition of the dEMG signal amplitude was seen within approximately 10 min. The mean magnitude of inhibition of the dEMG signal amplitude by DHA (25 mM) was almost equal to the local anesthetic, 1% lidocaine (37 mM), a sodium channel blocker. These findings suggest that DHA attenuates the nociceptive JOR via possibly blocking sodium channels, and strongly support the idea that DHA is a potential therapeutic agent and complementary alternative medicine for the prevention of acute trigeminal nociception.

Evaluation and validation of an automatic jaw movement recorder (RumiWatch) for ingestive and rumination behaviors of dairy cows during grazing and supplementation.

Observation of ingestive and rumination behaviors of dairy cows may assist in detecting diseases, controlling reproductive status, and estimating intake. However, direct observation of cows on pasture is time consuming and can be difficult to realize. Consequently, different systems have been developed to automatically record behavioral characteristics; among them is the RumiWatch System (RWS; Itin and Hoch GmbH, Liestal, Switzerland). Until now, the RWS has not been thoroughly validated under grazing conditions. The aim of the current study was to validate the RWS, against direct observation, in measuring ingestive and rumination behaviors of dairy cows during grazing and supplementation in the barn. A further objective was to examine whether it is possible to refine the algorithm used by the evaluation software RumiWatch Converter 0.7.3.2 to improve the accuracy of the RWS. The data were collected from an experiment carried out with 18 lactating Holstein cows in a crossover block design including 3 treatments and 3 measuring periods. All cows grazed night and day, 19 h/d, and were either unsupplemented or supplemented, with chopped whole-plant corn silage, or chopped whole-plant corn silage mixed with a protein concentrate. During the measuring periods, cows were equipped with the RumiWatch Halter, and their ingestive and rumination behaviors were recorded concurrently by the RumiWatch Halter and by direct observation (690 × 10 min). Comparison of concurrently measured data shows that the RWS detected jaw movements reliably, but classification errors occurred. A low relative prediction error of ≤0.10 for the number of rumination boluses, rumination chews, and total eating chews was found. A high relative prediction error of >0.10 was found for the number of prehension bites and time spent in prehension and eating. Both converter versions performed equally well in differentiating ingestive and rumination behaviors when cows were supplemented in the barn or when grazing and supplementation activities were combined. For grazing cows, with no supplementation, more reliable results for the total number of eating chews, rumination chews, prehension bites, and time spent in these activities were obtained, by using the RumiWatch Converter 0.7.3.11. In light of these findings, further research is warranted to improve the accuracy of the RWS and to allow a differentiation between mastication chews and prehension bites while eating.

Thalamo-insular pathway conveying orofacial muscle proprioception in the rat.

Little is known about how proprioceptive signals arising from muscles reach to higher brain regions such as the cerebral cortex. We have recently shown that a particular thalamic region, the caudo-ventromedial edge (VPMcvm) of ventral posteromedial thalamic nucleus (VPM), receives the proprioceptive signals from jaw-closing muscle spindles (JCMSs) in rats. In this study, we further addressed how the orofacial thalamic inputs from the JCMSs were transmitted from the thalamus (VPMcvm) to the cerebral cortex in rats. Injections of a retrograde and anterograde neuronal tracer, wheat-germ agglutinin-conjugated horseradish peroxidase (WGA-HRP), into the VPMcvm demonstrated that the thalamic pathway terminated mainly in a rostrocaudally narrow area in the dorsal part of granular insular cortex rostroventrally adjacent to the rostralmost part of the secondary somatosensory cortex (dGIrvs2). We also electrophysiologically confirmed that the dGIrvs2 received the proprioceptive inputs from JCMSs. To support the anatomical evidence of the VPMcvm-dGIrvs2 pathway, injections of a retrograde neuronal tracer Fluorogold into the dGIrvs2 demonstrated that the thalamic neurons projecting to the dGIrvs2 were confined in the VPMcvm and the parvicellular part of ventral posterior nucleus. In contrast, WGA-HRP injections into the lingual nerve area of core VPM demonstrated that axon terminals were mainly labeled in the core regions of the primary and secondary somatosensory cortices, which were far from the dGIrvs2. These results suggest that the dGIrvs2 is a specialized cortical region receiving the orofacial proprioceptive inputs. Functional contribution of the revealed JCMSs-VPMcvm-dGIrvs2 pathway to Tourette syndrome is also discussed.

Perturbed oral motor control due to anesthesia during intraoral manipulation of food.

Sensory information from periodontal mechanoreceptors (PMRs) surrounding the roots of natural teeth is important for optimizing the positioning of food and adjustment of force vectors during precision biting. The present experiment was designed to test the hypothesis; that reduction of afferent inputs from the PMRs, by anesthesia, perturbs the oral fine motor control and related jaw movements during intraoral manipulation of morsels of food. Thirty healthy volunteers with a natural dentition were equally divided into experimental and control groups. The participants in both groups were asked to manipulate and split a spherical candy into two equal halves with the front teeth. An intervention was made by anesthetizing the upper and lower incisors of the experimental group while the control group performed the task without intervention. Performance of the split was evaluated and the jaw movement recorded. The experimental group demonstrated a significant decrease in measures of performance following local anesthesia. However, there was no significant changes in the duration or position of the jaw during movements in the experimental and control group. In conclusion, transient deprivation of sensory information from PMRs perturbs oral fine motor control during intraoral manipulation of food, however, no significant alterations in duration or positions of the jaw during movements can be observed.

Systemic administration of the dietary constituent resveratrol inhibits the nociceptive jaw-opening reflex in rats via the endogenous opioid system.

The aim of the present study was to investigate whether, under in vivo conditions, systemic administration of resveratrol could attenuate the rat nociceptive jaw-opening reflex (JOR) via the endogenous opioid system. The JOR evoked by electrical stimulation of the tongue was recorded as digastric muscle electromyograms (dEMG) in pentobarbital-anesthetized rats. The amplitude of the dEMG increased significantly in proportion to the intensity of electrical stimulation (from 1× to 5 × threshold for the JOR). dEMG amplitude in response to 3× threshold electrical stimulation of the tongue was dose-dependently inhibited by intravenous administration of resveratrol (0.5-2mg/kg). Maximum inhibition of dEMG amplitude was seen within approximately 10min. These inhibitory effects were reversible, with dEMG responses returning to control levels after approximately 20min. Pretreatment of rats with naloxone resulted in significant, dose-dependent attenuation of the inhibitory effects of resveratrol on dEMG amplitude compared with control. These findings suggest that resveratrol inhibits the nociceptive JOR via the endogenous opioid system. Further, the findings of the present study strongly support the idea that resveratrol, which is not known to have any toxic side effects, combined with an opioid could be a potential therapeutic agent for the prevention of acute trigeminal nociception.

Effects of an Open Jaw Posture on Vowel Perception in the Aging Voice.

PURPOSE: This study aimed to verify through an auditory-perceptual approach, whether an "open jaw" posture would result in improved speech quality for older adults. METHODS: Forty normal-hearing listeners (20 males; 20 females) aged between 18 and 47 listened to vowel segments and performed two separate tasks: identifying vowels and comparing vowel clarity. Stimuli included vowels segmented from a sentence ("We saw two cars.") produced using a normal and an open jaw posture by 40 individuals aged between 30s and 80s. Three types of stimuli were presented: variable length and intensity, fixed length and variable intensity, and fixed length and normalized intensity. Mixed model analyses of variance were used to determine whether there was a jaw posture effect on the percentage of correct vowel identification. Chi-square tests were used to determine whether vowels produced with an open jaw posture were more likely to be identified as being "clearer." RESULTS: Open jaw posture resulted in higher rates of correct vowel identification, and vowels from contrast pairs were consistently judged as being "clearer" than vowels produced in normal jaw posture. Investigations on the effect of stimulus type revealed that the jaw-related improvement in speech quality was not solely due to an increase in intensity or length induced by an open jaw posture. CONCLUSIONS: Listeners assessing vowel identification and clarity in the aging voice were able to better differentiate among vowels spoken using an open jaw posture, and a greater number of vowels produced in an open jaw posture were perceived as sounding clearer.

Immediate Effects of Combining Local Techniques in the Craniomandibular Area and Hamstring Muscle Stretching in Subjects with Temporomandibular Disorders: A Randomized Controlled Study.

OBJECTIVE: To assess the immediate effects on vertical mouth opening, orofacial mechanosensitivity, and lumbar and suboccipital mobility after adding a myofascial induction technique to a multimodal protocol in subjects with temporomandibular disorders (TMD). DESIGN: A randomized and double-blind controlled trial was carried out. SETTINGS/LOCATION: University-based physical therapy research clinic. SUBJECTS: Sixty subjects (35±11.22 years) with TMD, and restricted mobility of the mandibular condyles and the first cervical vertebrae, were recruited and randomized to either a control group (CG) (n=30) or an experimental group (EG) (n=30). INTERVENTIONS: The CG underwent a neuromuscular technique over the masseter muscles and passive hamstring muscle stretching. A suboccipital muscle inhibition technique was added to this protocol in the EG. OUTCOME MEASURES: Primary measurements were made of vertical mouth opening and pressure pain threshold of the masseter muscles. Secondary outcome measures included pressure algometry of the trigeminal nerve, suboccipital range of motion, and lumbar spine mobility, assessed with the sit-and-reach (SAR) test and lumbar forward bending. All evaluations were collected at baseline and immediately after intervention. RESULTS: In the intragroup comparison, the EG observed an increase in suboccipital flexion (p<0.001; F1,29=14.47; R(2)=0.33) and the SAR test (p=0.009; F1,29=7.89; R(2)=0.21). No significant differences were found in the between-group comparison for any variable (p>0.05). CONCLUSION: The inclusion of a myofascial induction maneuver in a protocol combining local (neuromuscular treatment) and distal techniques (hamstring stretching) in subjects with TMD has no impact on improving mouth opening, suboccipital and lumbar mobility, and orofacial sensitivity to mechanical pressure.

Feeding biomechanics of the cownose ray, Rhinoptera bonasus, over ontogeny.

Growth affects the performance of structure, so the pattern of growth must influence the role of a structure and an organism. Because animal performance is linked to morphological specialization, ontogenetic change in size may influence an organism's biological role. High bite force generation is presumably selected for in durophagous taxa. Therefore, these animals provide an excellent study system for investigating biomechanical consequences of growth on performance. An ontogenetic series of 27 cownose rays (Rhinoptera bonasus) were dissected in order to develop a biomechanical model of the feeding mechanism, which was then compared with bite forces measured from live rays. Mechanical advantage of the feeding apparatus was generally conserved throughout ontogeny, while an increase in the mass and cross-sectional area of the jaw adductors resulted in allometric gains in bite force generation. Of primary importance to forceful biting in this taxon is the use of a fibrocartilaginous tendon associated with the insertion of the primary jaw adductor division. This tendon may serve to redirect muscle forces anteriorly, transmitting them within the plane of biting. Measured bite forces obtained through electrostimulation of the jaw adductors in live rays were higher than predicted, possibly due to differences in specific tension of actual batoid muscle and that used in the model. Mass-specific bite forces in these rays are the highest recorded for elasmobranchs. Cownose rays exemplify a species that, through allometric growth of bite performance and morphological novelties, have expanded their ecological performance over ontogeny.

Influence of an external rhythm on oral motor control in children and adults.

BACKGROUND: Rhythm has been used in music therapy practice to facilitate speech output in children and adults; however, the underlying mechanism of speech entrainment is not yet understood. OBJECTIVE: The purpose of this study was to (a) determine the feasibility of using the limb motor response model for testing oral motor entrainment and (b) establish initial data on oral motor entrainment across ages. METHODS: Six healthy 7- to 10-year-olds, six 11- to 14-year-olds, and twelve 18-35-year-olds served as participants. The oral motor kinematics of the upper lip, lower lip, and jaw were examined while participants repeated a bilabial syllable, recorded under three conditions: preferred tempo with no stimulus, preferred tempo with a rhythmic auditory stimulus, and 10% faster with a rhythmic auditory stimulus. The Spatiotemporal Index (STI) was computed to determine movement variability in each condition and the Synchronization Error (SE) was calculated to determine deviations from the auditory stimulus. RESULTS: Successful completion of the protocol by most participants and initial evidence of entrainment supported feasibility. There was a statistically significant difference in the STI for condition and marker placement. There were no significant differences for age. CONCLUSION: Oral motor entrainment of isolated syllables may be measured using the motor response model. Although data indicated that children and adults could entrain oral motor movements to the external auditory stimulus, the perceived tempo or the cognitive demands of such tasks may increase oral motor variability.

Low body mass index and jaw movement are protective of hearing in users of personal listening devices.

OBJECTIVES/HYPOTHESIS: Sound pressure level delivered through personal listening devices (PLDs) and reaching the ear drum might be affected by body size and jaw movements. This study aimed to investigate whether jaw movement and/or smaller body mass index (BMI) resulted in decrease of sound pressure level within the ear canals of PLD users via an earbud earphone. STUDY DESIGN: Case series. METHODS: Forty-five normal-hearing subjects (16 males; mean age, 23.3 years) participated in this study. A probe-microphone system was used to measure sound pressure level in the external ear canal with music delivered from a media player via an earbud earphone. Test materials consisted of two 20-second excerpts from a heavy metal music piece. Subjects were instructed to adjust the volume of the media player to conform to three conditions for sound pressure measurement: comfortable, loud, and maximum. Measurements were then repeated while subjects mimicked chewing action under the same listening conditions. RESULTS: Sound pressure levels were significantly lower when measured with jaw movement than without jaw movement (P < .05). Sound pressure levels monitored with/without jaw movement were generally lower in subjects with a BMI<23 than those with a BMI ≥ 23 (P < .05). CONCLUSIONS: Jaw movement and low BMI (<23) reduced the overall sound level of PLDs at the ear canal. Sound pressure levels detected in the external ear canal of our subjects using earbud earphones were significantly lower under conditions of jaw movement/BMI <23. Our research invites further studies on a larger group of PLD users to correlate these variables with hearing threshold shifts over time.

Brain activity associated with memory and cognitive function during jaw-tapping movement in healthy subjects using functional magnetic resonance imaging.

OBJECTIVE: To determine whether jaw-tapping movement, a classically described as an indication of personal well-being and mental health, stimulates the memory and the cognitive regions of the brain and is associated with improved brain performance. METHODS: Twelve healthy right-handed female subjects completed the study. Each patient performed a jaw-tapping task and an n-back task during functional magnetic resonance imaging (fMRI). The subjects were trained to carry out the jaw-tapping movement at home twice a day for 4 weeks. The fMRI was repeated when they returned. RESULTS: During the first and second jaw-tapping session, both sides of precentral gyrus and the right middle frontal gyrus (BA 6) were activated. And during the second session of the jaw-tapping task, parts of frontal lobe and temporal lobe related to memory function were more activated. In addition, the total percent task accuracy in n-back task significantly increased after 4 weeks of jawtapping movement. After jaw-tapping training for 4 weeks, brain areas related to memory showed significantly increased blood oxygen level dependent signals. CONCLUSION: Jaw-tapping movement might be a useful exercise for stimulating the memory and cognitive regions of the brain.

Myofascial trigger points in the masticatory muscles in patients with and without chronic mechanical neck pain.

OBJECTIVES: The purpose of this study is to describe differences in the presence of masseter and temporalis muscle trigger points (TrPs) and jaw opening between individuals with mechanical neck pain and healthy controls. METHODS: Twenty patients with mechanical neck pain (60% women) without symptoms in the orofacial region, aged 20 to 37 years old, and 20 matched controls participated. Temporalis and masseter muscles were examined for the presence of TrPs in a blinded design. Trigger points were considered active if the subject recognized the pain as a familiar symptom, whereas the TrPs was considered latent if the pain was not recognized as a symptom. Jaw opening was assessed with a ruler. RESULTS: A greater number (P < .001) of TrPs in the masticatory muscles were found in patients than in controls. None of the patients or healthy controls recognized the referred pain as familiar; thus, latent rather than active TrPs were found. The distribution of TrPs between groups was different for the masseter (left odds ratio [OR], 3.4; right OR, 8.1; P < .001) and temporalis (left OR, 2.8; right OR, 5.7; P < .001) muscles. Patients with neck pain had smaller jaw opening than controls (P < .001). A negative correlation between active jaw opening and the number of TrPs within the masticatory muscles (r(s) = -0.6; P < .001) was found: the greater the number of TrPs, the smaller the jaw opening. CONCLUSIONS: For the subjects in this study, those with mechanical chronic neck pain had more latent TrPs in the masticatory muscles and reduced jaw opening compared to healthy controls. These findings may suggest the spread of sensitization from the cervical segment to the trigeminal brain stem sensory nuclear complex.

Teriparatide and osseous regeneration in the oral cavity.

BACKGROUND: Intermittent administration of teriparatide, a drug composed of the first 34 amino acids of parathyroid hormone, has anabolic effects on bone. Although teriparatide has been evaluated for the treatment of osteoporosis and for the healing of fractures, clinical trials evaluating it for the treatment of osseous conditions of the oral cavity in humans are lacking. METHODS: A total of 40 patients with severe, chronic periodontitis underwent periodontal surgery and received daily injections of teriparatide (20 µg) or placebo, along with oral calcium (1000 mg) and vitamin D (800 IU) supplementation, for 6 weeks. The patients were followed for 1 year. The primary outcome was a radiographic linear measurement of alveolar bone level. Secondary outcomes included clinical variables, bone turnover markers in serum and oral fluid, systemic bone mineral density, and quality of life. RESULTS: Radiographic linear resolution of osseous defects was significantly greater after teriparatide therapy than after placebo beginning at 6 months, with a mean linear gain in bone at 1 year of 29% as compared with 3% (P<0.001). Clinical improvement was greater in patients taking teriparatide than in those taking placebo, with a reduction in periodontal probing depth of 33% versus 20% (2.42 mm vs. 1.32 mm) and a gain in clinical attachment level of 22% versus 7% (1.58 mm vs. 0.42 mm) in target lesions at 1 year (P = 0.02 for both comparisons). No serious adverse events were reported; however, the number of patients in the study was small. No significant differences were noted with respect to the other variables that were assessed. CONCLUSIONS: Teriparatide, as compared with placebo, was associated with improved clinical outcomes, greater resolution of alveolar bone defects, and accelerated osseous wound healing in the oral cavity. Teriparatide may offer therapeutic potential for localized bone defects in the jaw. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT00277706 .).

[Criteries of the regeneration intensity in bone jaw's tissue during treatment of inflammatory destructive processes].

Study of some biochemical parameters of oral fluid in patients with periapical jaws' inflammatory destructive processes in the process of operative treatment was conducted. It was established that dynamics of these indicators could be indirect criterion of permissive value of activity and completeness of bone tissue reparative regeneration processes. Advantage of the method is in its small invasiveness.

P2X and NMDA receptor involvement in temporomandibular joint-evoked reflex activity in rat jaw muscles.

We have previously shown that injection of the excitatory amino glutamate into the rat temporomandibular joint (TMJ) evokes reflex activity in both anterior digastric (DIG) and masseter (MASS) muscles that can be attenuated by prior TMJ injection of an N-methyl-d-aspartate (NMDA) receptor antagonist. The aim of the present study was to test if jaw muscle activity could also be evoked by P2X receptor agonist injection into the rat TMJ region and if the reflex activity could be modulated by TMJ injection of P2X receptor antagonist or NMDA receptor antagonist. The selective P2X subtype agonist alpha,beta-methylene adenosine 5'-triphosphate (alpha,beta-me ATP) and vehicle (phosphate-buffered saline) or the selective P2X antagonist, 2'-(or-3')-O-(2,4,6-trinitrophenyl) adenosine 5'-triphosphate (TNP-ATP) or the selective NMDA antagonist (+/-)-d-2-amino-5-phosphonovalerate(APV) were injected into the rat TMJ region. Electromyographic (EMG) reflex activity was recorded in both DIG and MASS muscles. Compared with the baseline EMG activity, alpha,beta-me-ATP injection into the TMJ (but not its systemic administration) following pre-injection of the vehicle significantly increased the magnitude and the duration of ipsilateral DIG and MASS EMG activity in a dose-dependent manner. The alpha,beta-me-ATP-evoked responses could be antagonized by pre-injection of TNP-ATP into the same TMJ site but contralateral TMJ injection of TNP-ATP proved ineffective. Furthermore, the alpha,beta-me-ATP-evoked responses could also be antagonized by APV injected into the same TMJ site but not by its systemic injection. These results indicate the interaction of peripheral purinergic as well as glutamatergic receptor mechanisms in the processing of TMJ nociceptive afferent inputs that evoke reflex activity in jaw muscles.