Search

Objectives this case-control study’s objective was to investigate variables based on a cognitive-behavioral-emotional model related to the development of painful temporomandibular disorders (TMD) in a sample of monozygotic twins discordant for the condition. Materials and Methods 20 monozygotic twins (10 pairs discordant for painful TMD), aged between 18 and 55 years, were studied. The diagnosis of painful TMD was determined according to the Diagnostic Criteria for Temporomandibular Disorders - Brazilian Portuguese (DC/TMD). The cognitive-behavioral-emotional variables analyzed were sociodemographic profile, pain sensitivity (pain threshold to pressure, allodynia, and hyperalgesia), oral behaviors, pain vigilance and awareness, pain catastrophizing, central sensitization, stress, anxiety, depression, alexithymia, mindfulness facets, sleep quality, pain control, pain intensity and interference, trigeminal and extratrigeminal pain areas. Results According to the adjusted regression model, there was an increased chance of TMD with: an increasing left-sided masseter face pain sensitivity score (OR = 3.29;95%CI=(0.17–62.8),p = 0.428); an increasing total pain catastrophizing score (OR = 1.08; 95%CI=(0.64–1.8),p = 0.776); an increasing score of difficulty in externalizing feelings (OR = 1.61;95%CI=(0.13–2.9),p = 0.539); and a scoring of the distraction facet of the FFMQ scale (OR = 4.65;95%CI=(0.39–55.7),p = 0.225). Conclusions from the cognitive-behavioral-emotional model studied in this case-control study of monozygotic twins discordant for painful TMD, painful sensitivity in the face, catastrophizing pain, difficulty in externalizing feelings, and the distraction facet (mindfulness) are variables that increase the chance of developing painful TMD. Clinical Relevance: This study with discordant monozygotic twins allows phenotype analyses, minimizing genetic and social influences. The results elucidate that cognitive-behavioral-emotional variables increase the chance of developing painful TMD, despite genetic influences.

Panic-like reactions elicited by electrical stimulation of the dorsal periaqueductal grey matter (ES-dPAG) seem to be regulated by dopamine (DA). We showed that DA applied intranasally (IN) increased escape-behaviour thresholds induced by ES-dPAG of rats, indicating a panicolytic-like effect.We investigated whether IN-DA increases escape-response thresholds induced by ES-dPAG by acting on DWistar rats exposed to ES-dPAG were treated with Sulpiride (SUL, 40 mg/kg, DAnti-aversive effects of the IN-DA were reduced by SUL pretreatment in the ES-dPAG test. IN-DA did not affect the escape number in the PSP nor the escape latencies in the ETM as well as motor performance in the OF.The IN-DA effects in reducing unconditioned fear responses elicited by ES-dPAG seem to be mediated by D

Photobiomodulation therapy (PTB) is a therapeutic possibility for temporomandibular disorders (TMD), but its effectiveness and protocols for use remain controversial. This study is a RCT that compared the effectiveness of PTB on pain points of the masticatory muscles and TMJs, located through palpation versus application of pre-established points in women with painful TMD, diagnosis by DC/TMD (Diagnostic Criteria for Temporomandibular Disorders - Brazilian Portuguese version). Therefore, a total sample of 54 women, aged between 18 and 60 years, was investigated. Volunteers were randomly randomized and PTB was applied in four different groups with a dose of 4 J and 6 J divided into pre-established application points (PE - G1) and pain points (PD - G2) - Groups 4PE, 4PD, 6PE and 6PD. Four laser applications were performed with a wavelength of 780 nm, one session per week, totaling one month of therapy. The following assessments were performed: DC/TMD, Brief Pain Inventory (BPI), McGill Questionnaire - Short Version (SF-MPQ) and Pain Intensity, Visual Analogue Scale (VAS). Friedman's test was used for within-group comparisons, while the Mann-Whitney test was used for between-group comparisons (p 0.05). According to the results, laser application on pain points (G2) was more effective. McGill's results showed that regardless of dose, the pain point application group had better outcomes (p = 0.004). Pain intensity evaluation (last days) also showed that application at the pain points was more effective regardless of dose (p = 0.0002). Medians and interquartile deviations showed overall that PTB was more effective at pain points, with a trend towards better outcomes at the 6 J dose. Therefore, it can be concluded that in women with chronic painful TMD, the application of PTB at pain points is more effective than the application at pre-established points. Therefore, individualized PTB protocols are proposed, based on examination palpation of the masticatory structures.

Temporomandibular disorder (TMD) is characterized by acute or chronic orofacial pain, which can be associated with inflammatory processes in the temporomandibular joint (TMJ) and emotional disorders. Peripheral and central sensitization in painful orofacial processes is common, and it can be triggered by peripheral inflammatory challenge with consequent neuroinflammation phenomena. Such neuroinflammation comes from inflammatory products from supportive cells, blood-brain barrier, and extracellular matrix. Here, we evaluated the possible recruitment of limbic structures for modified matrix metalloproteinases (MMPs) expression and activity during temporomandibular inflammation-induced orofacial persistent pain. The inflammatory process in TMJs of rats was induced by Freund's Complete Adjuvant (CFA) administration. The activity and expression of MMPs-2 and 9 were assessed by in situ zymography and conventional zymography, respectively. A glial colocalization with the MMPs was performed using immunofluorescence. The results evidenced both short- and long-term alterations on MMP-2 and -9 expression in the limbic structures following CFA-induced temporomandibular inflammation. The gelatinolytic activity was increased in the central amygdala, hippocampus, hypothalamus, ventrolateral periaqueductal gray (vlPAG), superior colliculus, and inferior colliculus. Finally, an increase of colocalization of MMP-2/GFAP and MMP-9/GFAP in CFA-induced inflammation groups was observed when compared with saline groups in the central amygdala and vlPAG. It is possible to suggest that glial activation is partly responsible for the production of gelatinases in the persistent orofacial pain, and it is involved in the initiation and maintenance of this process, indicating that inhibition of MMPs might be pursued as a potential new therapeutic target for TMD.

Objetivo: analisar parâmetros clínicos sugestivos de sensibilização central em mulheres com disfunção temporomandibular dolorosa crônica antes e após uma intervenção baseada em mindfulness. Método: onze mulheres com idade entre 27 e 44 anos (36,36 ± 5,61), com diagnóstico de disfunções temporomandibulares dolorosa crônica (Diagnostic Criteria for Temporomandibular Disorders),participaram do estudo. A hiperalgesia, a alodinia e o limiar de dor à pressão foram avaliados em pontos trigeminais e extra-trigeminais antes e após a intervenção baseada em mindfulness, bem como a aplicação do questionário Mindful Attention Awareness Scale. O programa de mindfulness de 8 semanas foi oferecido às participantes do estudo, com base no protocolo Mindfulness Trainings International, em sessões semanais de 2 horas e uma sessão de 4 horas. Resultados: houve redução significativa da alodinia, da hiperalgesia e aumento do limiar de dor à pressão, além de aumento significativo do nível de atenção plena (p < 0,05) enquanto marcador de efetividade da intervenção baseada em mindfulness oferecida. Conclusão: índices mais saudáveis nos parâmetros clínicos sugestivos de sensibilização central investigados após a intervenção, representam melhora significativa na relação da pessoa com quadro de enfermidade crônica geradora de experiências desagradáveis contínuas como a disfunções emporomandibulares.

Background: Panic-like reactions elicited by electrical stimulation of the dorsal periaqueductal grey matter (ES-dPAG) seem to be regulated by dopamine (DA). We showed that DA applied intranasally (IN) increased escape-behaviour thresholds induced by ES-dPAG of rats, indicating a panicolytic-like effect. Aims: We investigated whether IN-DA increases escape-response thresholds induced by ES-dPAG by acting on D2-like receptors, and whether IN-DA affects escape responses elicited by the presence of a potential predator and by open space and height of the elevated T-maze (ETM) as well as motor performance in the open field (OF) test. Methods: Wistar rats exposed to ES-dPAG were treated with Sulpiride (SUL, 40 mg/kg, D2-like receptor antagonist) previously IN-DA (2 mg/kg). Independent groups of rats treated with IN-DA were submitted to prey versus snake paradigm (PSP), ETM and OF. Results: Anti-aversive effects of the IN-DA were reduced by SUL pretreatment in the ES-dPAG test. IN-DA did not affect the escape number in the PSP nor the escape latencies in the ETM as well as motor performance in the OF. Conclusions/interpretation: The IN-DA effects in reducing unconditioned fear responses elicited by ES-dPAG seem to be mediated by D2-like receptors. The lack of effects on panic-related responses in the ETM and PSP may be related to the possibility of avoiding the danger inherent to these models, a defence strategy not available during ES-dPAG. These findings cannot be attributed to motor performance. The decision-making responses to avoid dangerous situations can be orchestrated by supra-mesencephalic structures connected by non-dopaminergic inputs.

Pain catastrophizing has dimensions of magnification, rumination, and helplessness, being an important evaluator of chronic pain. Studies with mindfulness intervention point to a possible modulation of chronic pain catastrophizing behavior. However, how these facets of mindfulness are associated with the catastrophizing subscales is uncertain. The scope of this study is to verify how the association of mindfulness facets and catastrophizing subdimensions occurs.Women with chronic TMD answered the Pain Catastrophizing Scale (PCS) and Five Facets of Mindfulness Questionnaire (FFMQ).Magnification was inversely correlated with "not reacting," "not judging," and the total FFMQ score. Total PCS was also inversely correlated with "not reacting."It is necessary to consider such possible correlations between mindfulness facets and the catastrophizing subdimensions in mindfulness-based interventions for this population.

The mechanisms underlying temporomandibular disorders following orofacial pain remain unclear. Hydrogen sulfide (H2S), a newly identified gasotransmitter, has been reported to modulate inflammation. Cystathionine γ-lyase (CSE) is responsible for the systemical production of H2S, which exerts both pro- and antinociceptive effects through inflammation. In the current study, we investigated whether the endogenous H2S production pathway contributes to arousal and maintenance of orofacial inflammatory pain, through the investigation of the effects of a CSE inhibitor, propargyglycine (PAG), in a rat CFA (Complete Freund Adjuvant)-induced temporomandibular inflammation model to mimic persistent pain in the orofacial region. For this, rats received either CFA or saline in the temporomandibular joints (TMJs), and after 3 or 14 days, they received a single injection of PAG or saline and were evaluated for nociception with the von Frey and formalin test. Also, pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) were analyzed in TMJs and trigeminal ganglion (TG). In this last one, glial cells reactivity was also verified. Endogenous H2S production rate were measured in both, TMJ and TG. Our results indicated decreased allodynia and hyperalgesic responses in rats submitted to CFA after injection of PAG. Moreover, PAG inhibited leucocyte migration to temporomandibular synovial fluid after 3 and 14 days of inflammation. PAG was able to reduce levels of CBS, CSE, TNF-α, and IL-1β in the TMJ and TG, after 13 days of CFA injection. The observed increased activation of glial cells in the trigeminal ganglia on the 14th day of inflammation can be prevented by the highest dose of PAG. Finally, CBS and CSE expression, and endogenous H2S production rate in the TMJ and TG was found higher in rats with persistent temporomandibular inflammation compared to rats injected with saline and PAG was able to prevent this elevation. Our results elucidated the molecular mechanisms by which H2S exerts its pro-inflammatory and pro-nociceptive role in the orofacial region by alterations in both local tissue and TG.

Accurate diagnosis and treatment of pain is dependent on knowledge of the variables that might alter this response. Some of these variables are the locality of the noxious stimulus, the sex of the individual, and the presence of chronic diseases. Among these chronic diseases, hypertension is considered a serious and silent disease that has been associated with hypoalgesia. The main goal of this study was to evaluate the potential nociceptive differences in spontaneously hypertensive rats (SHR) regarding the locality of the stimulus, i.e., the temporomandibular joint or paw, the sex, and the role of ovarian hormones in a model of mechanical nociception (Von Frey test) or formalin-induced inflammatory nociception. Our results indicate that SHR had lower orofacial mechanical nociception beyond the lower mechanical nociception in the paw compared with WKY rats. In a model of formalin-induced inflammatory nociception, SHR also had decreased nociception compared with normotensive rats. We also sought to evaluate the influence of sex and ovarian hormones on orofacial mechanical nociception in SHR. We observed that female SHR had higher mechanical nociception than male SHR only in the paw, but it had higher formalin-induced orofacial nociception than male SHR. Moreover, the absence of ovarian hormones caused an increase in mean arterial pressure and a decrease in paw nociception in female SHR.

Objective: Animal models of chronic pain have demonstrated that glial cells are promising target for development of analgesic drugs. However, preclinical studies on glial response under chronic pain conditions vary depending on the cellular markers, the species used, the experimental design and model. Therefore, we investigate the expression profile of GFAP and Iba-1 during the behavioral manifestation of sensory disorder in inflammatory and neuropathic pain models. Methods: the expression profile of fibrillary acidic protein (GFAP) and ionized calcium binding adaptor molecule-1 (Iba-1) were quantitated in the spinal dorsal horn of Balb/C mice submitted to six models of chronic pain. Protein analysis was performed by western blot and the results colligated with pain-related behavior. Results: Using the same method to quantitate proteins we observed that while GFAP is upregulated after axotomy, partial nerve injury and cutaneous inflammation, its expression is not changed during muscle inflammation, non-inflammatory muscle pain, and in a viral-associated pain. Differently, Iba-1 is downregulated after axotomy but upregulated after partial lesion of peripheral nerve as well as after virus inoculation and during non-inflammatory muscle pain. Cutaneous and muscle inflammation induced no change in Iba-1 expression in the dorsal horn.In spite of a marked time-dependent variation in protein expression, mechanical allodynia was present at any time of all the models investigated. Discussion: Under distinct pain conditions, GFAP and Iba-1 expression is dependent on the origin of the stimulus, disease progression and tissue affected. Moreover, their expression and is not necessarily associated to the behavior manifestation of pain.

Tonic immobility (TI) is a temporary state of profound motor inhibition associated with great danger as the attack of a predator. Previous studies carried out in our laboratory evidenced high Fos-IR in the posteroventral region of the medial nucleus of the amygdala (MEA) after induction of the TI response. Here, we investigated the effects of GABAA and GABAB of the MEA on TI duration. Intra-MEA injections of the GABAA agonist muscimol and GABAB agonist baclofen reduced TI response, while intra-MEA injections of the GABAA antagonist bicuculline and GABAB antagonist phaclofen increased the TI response. Moreover, the effects observed with muscimol and baclofen administrations into MEA were blocked by pretreatment with bicuculline and phaclofen (at ineffective doses per se). Finally, the activation of GABAA and GABAB receptors in the MEA did not alter the spontaneous motor activity in the open field test. These data support the role of the GABAergic system of the MEA in the modulation of innate fear.

Psychological stress and occlusal alterations are contributing etiologic factors for temporomandibular and muscular disorders in the orofacial area. The neural modulation recruited for this relationship, however, is not elucidated. The aim of this study was to investigate potential central mechanisms involved in the exodontia-induced occlusal instability associated with unpredictable chronic stress (UCS). Male adult Wistar rats were submitted to occlusal instability (unilateral molar teeth extraction) and/or to a UCS protocol and treated with diazepam or vehicle. The anxiety-like behavior was evaluated by elevated plus maze (EPM) and open field (OF) tests. Limbic structures such as the central nucleus of the amygdala (CeA), paraventricular nucleus of the hypothalamus (PVN), dorsal periaqueductal gray matter (dPAG) and nucleus accumbens core (NAc) were analyzed for expression of FosB/ΔFosB (immediate early genes) by immunohistochemistry. Exodontia and/or UCS decreased the time spent in the open arms at the EPM and the distance travelled at the OF, and increased the immobility time at the OF, suggesting anxiety-like behavior. In addition, exodontia induction resulted in an upregulation of FosB/ΔFosB in the CeA, PVN and dPAG, while UCS and exodontia + UCS upregulate FosB/ΔFosB immunoreactivity in the CeA, PVN, dPAG and NAc. Treatment with diazepam decreased the expression of FosB/ΔFosB in all analyzed structures of animals subject to UCS and exodontia + UCS, while promoted a reduction in the FosB/ΔFosB expression in the CeA, PVN and dPAG in animals subject to exodontia. Our findings showed an anxiogenic effect of exodontia and UCS, which is correlated with intranuclear neuron activation of limbic structures in a spatially dependent manner and that is prevented by the administration of diazepam.

The incidence of chronic pain is high in the general population and it is closely related to anxiety disorders, which promote negative effects on the quality of life. The cannabinoid system has essential participation in the pain sensitivity circuit. In this perspective, cannabidiol (CBD) is considered a promising strategy for treating neuropathic pain. Our study aimed to evaluate the effects of sub-chronic systemic treatment with CBD (0.3, 3, 10, or 30 mg/kg, i.p.) in male in rats submitted to chronic constriction injury of the sciatic nerve (CCI) or not (SHAM) and assessed in nociceptive tests (von Frey, acetone, and hot plate, three days CBD's treatment) and in the open field test (OFT, two days CBD's treatment). We performed a screening immunoreactivity of CB1 and TRPV1 receptors in cortical and limbic regions tissues, which were collected after 1.5 h of behavioral tests on the 24th experimental day. This study presents a dose-response curve to understand better the effects of low doses (3 mg/kg) on CBD's antiallodynic and anxiolytic effects. Also, low doses of CBD were able to (1) reverse mechanical and thermal allodynia (cold) and hyperalgesia, (2) reverse anxious behaviors (reduction of the % of grooming and freezing time, and increase of the % of center time in the OFT) induced by chronic pain. The peripheral neuropathy promoted the increase in the expression of CB1 and TRPV1 receptors in the anterior cingulate cortex (ACC), anterior insular cortex (AIC), basolateral amygdala (BLA), dorsal hippocampus (DH), and ventral hippocampus (VH). CBD potentiated this effect in the ACC, AIC, BLA, DH, and VH regions. These results provide substantial evidence of the role of the ACC–AIC–BLA corticolimbic circuit, and BLA-VH for pain regulation. These results can be clinically relevant since they contribute to the evidence of CBD's beneficial effects on treating chronic pain and associated comorbidities such as anxiety.

Cannabidiol (CBD) is a marijuana compound implicated in epilepsy treatment in animal models and pharmacoresistant patients. However, little is known about chronic CBD administration's effects in chronic models of seizures, especially regarding its potential antiepileptogenic effects. In the present study, we combined a genetic model of epilepsy (the Wistar Audiogenic Rat strain - WARs), a chronic protocol of seizures (the audiogenic kindling - AuK), quantitative and sequential behavioral analysis (neuroethology), and microscopy imaging to analyze the effects of chronic CBD administration in a genetic model of epilepsy. The acute audiogenic seizure is characterized by tonic-clonic seizures and intense brainstem activity. However, during the AuK WARs can develop limbic seizures associated with the recruitment of forebrain and limbic structures. Here, chronic CBD administration, twice a day, attenuated brainstem, tonic-clonic seizures, prevented limbic recruitment, and suppressed limbic (kindled) seizures, suggesting CBD antiepileptogenic effects. Additionally, CBD prevented chronic neuronal hyperactivity, suppressing FosB immunostaining in the brainstem (inferior colliculus and periaqueductal gray matter) and forebrain (basolateral amygdala nucleus and piriform cortex), structures associated with tonic-clonic and limbic seizures, respectively. Chronic seizures increased cannabinoid receptors type 1 (CB1R) immunostaining in the hippocampus and the BLA, while CBD administration prevented changes in CB1R expression induced by the AuK. The neuroethological analysis provided details about CBD's protective effects against brainstem and limbic seizures associated with FosB expression. Our results strongly suggest chronic CBD anticonvulsant and antiepileptogenic effects associated with reduced chronic neuronal activity and modulation of CB1R expression. We also support the chronic use of CBD for epilepsies treatments.

Carbon monoxide (CO) and nitric oxide (NO) modulate inflammatory nociception and anxiety. We evaluate whether treatments with a heme oxygenase-1 (HO-1) inducer (CoPP) or a carbon monoxide-releasing molecule (CORM-2) are capable of inhibiting inflammatory pain aversiveness in wild type (WT) and inducible nitric oxide synthase-knock out (NOS2-KO) mice with persistent inflammation and its relationship with μ- (MOR) and δ- (DOR) opioid receptors. WT and NOS2-KO male mice with complete Freund's adjuvant (CFA) injected into the hind paw were evaluated in the von Frey and the escape-avoidance paradigm (PEAP) tests, at 10 days, before and after the treatment with CORM-2 (5 mg/kg) or CoPP (2.5 mg/kg). WT mice groups treated with CORM-2 or CoPP also received naloxone (NLX, a non-specific opioid receptor antagonist). The HO-1, neuronal nitric oxide synthase, NOS2, MOR, and DOR expression in the dorsal hippocampus were evaluated by western blot. CFA reduced mechanical threshold in WT and NOS2-KO mice but only increased the percentage of time in the light compartment in the PEAP in WT mice. CORM-2 and CoPP inhibited these effects in both strains. Pre-treatment with NLX reverses the anti-allodynic and anti-aversive effects of CORM-2 or CoPP in WT mice. CORM-2 and CoPP increases the protein levels of HO-1, MOR and DOR in the dorsal hippocampus of WT mice but not in NOS2-KO animals. Results showed that HO CO pathway activation promotes anti-allodynic effects and reduced pain aversiveness caused by peripheral inflammation by increasing the expression of MOR and DOR activated by HO-1 in the dorsal hippocampus.

Stress is associated with orofacial pain sensitivity and is qualified as a temporomandibular disorder risk factor. During stressful periods, painful thresholds of masticatory muscles in individuals suffering muscle facial pain are significantly lower than in controls, but the exact physiologic mechanism underlying this relation remains unclear. Our hypothesis is that chronic unpredictable stress and masticatory hypofunction induce morphologic and metabolic masseter muscle changes in rats. For test this hypothesis, adult Wistar rats were submitted to chronic unpredictable stress and/or exodontia of left molars and the left masseter muscle was removed for analysis. The parameters evaluated included ultrastructure, oxidative level, metabolism activity and morphological analysis in this muscle. Our data show by histological analysis, that stress and exodontia promoted a variation on diameters and also angled contours in masseter fibers. The masticatory hypofunction increased oxidative metabolism as well as decreased reactive species of oxygen in masseter muscle. The ultrastructural analysis of muscle fibers showed disruption of the sarcoplasmic reticulum cisterns in certain regions of the fiber in stress group, and the disappearance of the sarcoplasmic reticulum membrane in group with association of stress and exodontia. Our findings clarify mechanisms by which chronic stress and masticatory hypofunction might be involved in the pathophysiology of muscular dysfunctions. Masticatory hypofunction influenced oxidative stress and induced oxidative metabolism on masseter muscle, as well as altered its fiber morphology. Chronic stress presented malefic effect on masseter morphology at micro and ultra structurally. When both stimuli were applied, there were atrophic fibers and a complete mitochondrial derangement.

Psychological stress and occlusal alteration are important etiologic factors for temporomandibular/masticatory muscular disorders. In particular, the exact physiologic mechanism underlying the relation by occlusal alteration and temporomandibular disorders remains unclear. Our purpose was to test the hypothesis that benzodiazepine therapy is able to prevent metabolic and vascular changes in the medial pterygoid muscle of rats under chronic stress after 14 days of unilateral exodontia. Adult Wistar rats were submitted to unpredictable chronic mild stress (10 days) and/or unilateral exodontia and their plasma and medial pterygoid muscles were removed for analysis. A pre-treatment with diazepam was used to verify its effect on stress. The parameters evaluated included anxiety behavior, plasma levels of corticosterone, metabolic activity by succinate dehydrogenase, capillary density by laminin staining and ultrastructural findings by transmission electron microscopy. Occlusal instability induced anxiety-like behavior on elevated plus-maze test and diazepam administration blocked the appearance of this behavior. Unilateral exodontia promoted in the contralateral muscle an increase of oxidative fibers and capillaries and modification of sarcoplasmic reticulum. Chronic stress caused increased glycolytic metabolism, reduced capillary density and morphological changes in mitochondria on both sides. Association of both factors induced a glycolytic pattern in muscle and hemodynamic changes. Pharmacological manipulation with diazepam inhibited the changes in the medial pterygoid muscle after stress. Our results reveal a preventive benzodiazepine treatment for stress and occlusal instability conditions affecting masticatory muscle disorders. In addition, provide insights into the mechanisms by which chronic stress and exodontia might be involved in the pathophysiology of masticatory muscular dysfunctions.

Tonic immobility (TI) is an innate defensive response exhibited by prey when physical contact with a predator is prolonged and inescapable. This defensive response is able to activate analgesia mechanisms; this activation has adaptive value because, during an attack by a predator, the manifestation of recuperative behaviors can affect the appropriate behavioral defense strategy. Some studies have suggested that similar structures of the central nervous system can regulate the response of both TI and nociception. Thus, this study evaluated the effect of chemical lesion through the administration of ibotenic acid in restricted brain areas of the periaqueductal gray matter (PAG) in guinea pig on the TI response and nociception evaluated in the hot plate test before and after emission of TI. The data showed that an irreversible chemical lesion in the ventrolateral PAG reduced of the TI response as well as defensive antinociception. However, a lesion in the dorsal PAG blocked the defensive antinociception induced by TI but did not alter TI duration. In summary, one could hypothesize that the neural substrates responsible for defensive behavior and antinociception represent similar systems that are distinct in modulation. Thus, the ventrolateral PAG has been associated with the modulation of TI and the defensive antinociception induced by TI. In contrast, the integrity of the dorsal PAG should be necessary for defensive antinociception to occur but not to elicit TI behavior in guinea pigs.

Studies have used paradigms based on animal models to understand human emotional behavior because they appear to be correlated with fear- and anxiety-related defensive patterns in non-human mammals. In this context, tonic immobility (TI) behavior is an innate response associated with extreme threat situations, such as predator attack. Some reports have demonstrated the involvement of corticotropin-releasing factor (CRF) in regulation of the endocrine system, defensive behaviors and behavioral responses to stress. Particularly, a previous study showed that the activation of CRF receptors in the basolateral (BLA) or central (CeA) nuclei of the amygdala increased TI responses, whereas treatment with a non-selective CRF antagonist, alpha-helical-CRF9-41, decreased this innate fear response. However, while CRF1 receptors have pronounced effects in stress-induced anxiety, CRF2 receptors appear be involved in the expression of both stress-induced anxiety and spontaneous anxiety behavior. In this study, we investigated the effects of specific CRF receptors, CRF1 and CRF2, in the BLA and CeA on the duration of TI in guinea pigs. The results show that blockade of CRF1 and CRF2 receptors in the BLA and CeA produces a decrease in fear and/or anxiety, as suggested by a decrease in TI duration in the guinea pigs. Additionally, the specific antagonists for CRF1 and CRF2 receptors were able to prevent the increase in TI duration induced by CRF administration at the same sites. These results suggest that the modulation of fear and anxiety by the CRF system in the BLA and CeA occurs through concomitant effects on CRF1 and CRF2 receptors.

Hydrogen sulfide (H2S), an endogenous gaseous mediator, modulates many physiological functions in mammals but evidence of its involvement in emotional and behavioral aspects is currently scarce. We hypothesized that this gas plays a modulatory role in behavioral parameters in rats submitted to tests (for 5min) in the open field (OF) and elevated plus-maze (EPM - test and retest). Male Wistar rats (200-250g) were intraperitoneally injected with saline or Na2S (a H2S donor; 4, 8 and 12mg/kg) either once or for 8days, and submitted to the OF test or to the EPM test and retest. A third group (naive) was not injected but exposed to the same experimental protocols. In the OF test, Na2S injected for 8days caused a decrease in self-cleaning (4, 8 and 12mg/kg) and freezing behaviors (8 and 12mg/kg), and a rise in the rate of line crossings in the central part of the arena (12mg/kg). In the EPM test and retest, Na2S at 12mg/kg for 8days caused an increase in the number of open arm entries and in the percentage of time spent on open arms. Our data are consistent with the notion that H2S exerts anxiolytic-like effects in rats submitted to the EPM and OF tests. Moreover, this gaseous modulator reduces aversive learning in the EPM retest.

Objective: To characterize short- and long-term assessment of the low-intensity laser therapy (LLLT) effectiveness in women with TMD of muscular origins and to evaluate whether the information abou...

Purpose:Intranasally applied dopamine (IN-DA), which likely reaches the brain via nasal–brain pathways and bypasses the blood–brain barrier, has been found to increase extracellular DA and bind to the DA2 transporter in the striatum. Recent studies suggest that DA plays a significant role in the processing of signaled and unconditioned aversive stimulation, including evidence that may attenuate responses to painful input. The purpose of this study was to examine the effects of IN-DA on fear-related behaviors induced by electric shock to the foot or by electrical stimulation of the dorsal periaqueductal gray matter (dPAG).Methods:DA hydrochloride suspended in a viscous castor oil gel (1 or 2 mg/kg) was applied (IN-DA) in a volume of 5 μL into the nostrils of adult Wistar male rats in order to evaluate its effects on (a) freezing induced by electric shock to the foot and (b) thresholds of freezing and escape and duration of post-stimulation freezing induced by electrical stimulation of the dPAG.Results:IN-DA attenuated freezing induced by electric shock to the foot in the three test trials, indicating that it reduced long-term fear responses. IN-DA also increased the threshold of dPAG stimulation-induced escape responses and reduced post-stimulation freezing.Conclusions:IN-DA, which has previously been shown to facilitate learning and to have antidepressive-like effects, attenuated unconditioned fear responses elicited by peripheral and intramesencephalic (dPAG) stimulation and reduced long-term conditioned fear responses.

Sepsis-associated encephalopathy (SAE) is a significant problem in patients with sepsis, and it is associated with a decrease in cognitive and sensitivity capability induced by systemic inflammation. SAE is implicated in reversible brain damage of several regions related to cognition, emotion, and sensation; however, it is not well established if it could affect brain regions associated with nociceptive modulation. Here were evaluated the nociceptive thresholds in rats with systemic inflammation induced by cecal ligation puncture (CLP). After 24 h of CLP, it was observed an increase in nociceptive threshold in all tests. Periaqueductal gray, rostroventral medulla, critical regions for descending nociceptive modulation, were evaluated and showed enhanced pro-inflammatory cytokines as well as glial activation. These results suggest that systemic inflammation could compromise descending facilitatory pathways, impairing nociceptive sensory functioning.

Rocio virus (ROCV) is a highly neuropathogenic mosquito-transmitted flavivirus responsible for an unprecedented outbreak of human encephalitis during 1975–1976 in Sao Paulo State, Brazil. Previous studies have shown an increased number of inflammatory macrophages in the central nervous system (CNS) of ROCV-infected mice, implying a role for macrophages in the pathogenesis of ROCV. Here, we show that ROCV infection results in increased expression of CCL2 in the blood and in infiltration of macrophages into the brain. Moreover, we show, using CCR2 knockout mice, that CCR2 expression is essential for macrophage infiltration in the brain during ROCV infection and that the lack of CCR2 results in increased disease severity and mortality. Thus, our findings show the protective role of CCR2-mediated infiltration of macrophages in the brain during ROCV infection., Rocio virus (ROCV) is a highly neuropathogenic mosquito-transmitted flavivirus responsible for an unprecedented outbreak of human encephalitis in Brazil. Here, we show that infiltrated macrophages in the brain may be protective in the pathogenesis of ROCV in a mouse model.

The aim of this study was to evaluate the transitory stress levels and the anxiety state in children submitted to conventional and computerized dental anesthesia. Twenty children (7 to 12 years) were randomly assigned to receive conventional and computerized dental anesthesia. To investigate the hypothesis that transitory stress could be lower after using computerized anesthesia compared to conventional anesthesia, cortisol levels in saliva were measured before and after each technique. Anxiety was also evaluated individually by answering the State-Trait Anxiety Inventory for Children (STAIC). Numerical data were analyzed statistically by the Mann-Whitney non-parametric test (5% significance level). Salivary cortisol levels increased in 8 (40%) patients after conventional anesthesia and in 9 (45%) patients after computerized anesthesia, with no statistically significant difference between the two types (p=0.34). In the same way, no statistically significant difference was found between the techniques (p=0.39) related to the psychological analysis based on the STAIC scores. Local anesthesia using either conventional anesthesia or a computerized delivery system produced similar level of stress/anxiety in pediatric patients, using both quantitative and qualitative analyses. O objetivo deste estudo foi avaliar os níveis de estresse transitório e o estado de ansiedade em crianças submetidas à anestesia dental convencional e computadorizada. Vinte crianças (7 a 12 anos de idade) foram randomicamente designadas para receber anestesia dental convencional e computadorizada. Para investigar a hipótese que o estresse transitório poderia ser menor após a anestesia computadorizada, comparada à anestesia convencional, os níveis de cortisol na saliva foram medidos antes e depois de cada técnica. A ansiedade também foi avaliada individualmente por meio do State-Trait Anxiety Inventory for Children (STAIC). Os dados numéricos foram analisados estatisticamente pelo teste não paramétrico de Mann-Whitney (nível de significância de 5%). Os níveis salivares de cortisol aumentaram em 8 (40%) pacientes após anestesia convencional e em 9 (45%) pacientes após anestesia computadorizada, sem diferença estatisticamente significante entre os dois tipos (p=0,34). Da mesma maneira, não foi encontrada diferença estatisticamente significante entre as técnicas (p=0,39) com relação à análise psicológica baseada nos escores STAIC. Anestesia local usando tanto a anestesia convencional quanto o sistema de aplicação computadorizado produziu nível similar de estresse/ansiedade em pacientes infantis, utilizando análises quantitativa e qualitativa.

Some researchers have shown that carbon monoxide (CO) plays a role in emotional behavior modulation through intracellular 3 '-5 '-guanosine monophosphate mechanisms in the locus coeruleus (LC). In fact, the LC region has a high expression of the heme-oxygenase (HO) enzymes, which are responsible for the production of CO. However, the physiological mechanism by which the HO-CO pathway participates in the modulation of emotional responses in the LC still needs clarification. This study evaluates whether a systemic intraperitoneal treatment is able to alter behavioral responses (in the elevated plus-maze and the light-dark box test) and the expression of the HO-1 and HO-2 enzymes in the LC. The tested treatments are acute (3 h before) or chronic (twice daily for 10 days) and with a carbon monoxide releaser (tricarbonyldichlororuthenium [II] dimer, or CORM-2) or with a HO-1 inducer compound (cobalt protoporphyrin IX, CoPP). The results for the elevated plus maze show that CO for both acute or chronic administration of either drug ncreased the number of entries into the open arms and the percentage of time spent in the open arms. Regarding the light-dark box test, chronic treatment with either drug increased the time spent in the light compartment. Additionally, treatment with CORM-2 or CoPP, either acutely or chronically, increased HO-1 enzyme expression in the LC cells. This study shows that systemic CO treatment can promote an anxiolytic-like effect and the expression of HO-1 enzymes in LC cells.

The aim was to analyze the non-specific effects (placebo, spontaneous remission, and regression to the mean) of the low-level laser therapy (LLLT) in women with myofascial pain (painful temporomandibular disorder (TMD)), as well as to differentiate between responders and non-responder clusters to active and placebo LLLT according to the anxiety levels, salivary cortisol, use of oral contraceptives, and premenstrual period. Sixty-four women diagnosed with myofascial pain (Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD)) were included, divided into laser (n = 20), placebo group (n = 21), and 23 controls (without treatment (WT)). The LLLT applied was 780 nm, masseter and temporal = 5 J/cm2 (20 mW–0.5 W/cm2), and TMJ area = 7.5 J/cm2 (30 mW–0.8 W/cm2), eight sessions, twice a week. The pain intensity (visual analogue scale (VAS)), anxiety (Beck Anxiety Inventory), salivary cortisol, and menstrual cycle’s data at the baseline, T1–T8, and 30 days after LLLT (follow-up) were evaluated. The laser group showed 80% of pain reduction, placebo 85%, and WT 43% in T8. Women with severe anxiety and at the premenstrual period did not reduce pain with any LLLT. Active and placebo LLLT had similar effectiveness during the treatment period; however, women with moderate anxiety, cortisol levels above 10 ng/ml, and without contraceptive use maintain analgesia longer with active LLLT than placebo (follow-up 30 days). Women with low levels of anxiety, salivary cortisol below 10 ng/ml, and with contraceptive use showed the higher pain reduction. The analgesia promoted by LLLT in women with myofascial pain is a result of non-specific effects during the treatment period, although active LLLT is more effective in maintaining the analgesia after treatment (30 days) for the cluster of women with moderate anxiety, salivary cortisol above 10 ng/ml, and without contraceptive use.

Hydrogen sulfide (H2S) is an endogenous neuromodulator produced mainly by the enzyme cystathionine gamma-lyase (CSE) in peripheral tissues. A pronociceptive role of endogenously produced H2S has been previously reported by our group in a model of orofacial inflammatory pain. Using the established persistent orofacial pain rat model induced by complete Freund's adjuvant (CFA) injection into temporomandibular joint (TMJ), we have now investigated the putative role of endogenous H2S modulating hypernociceptive responses. Additionally, plasmatic extravasation on TMJ was measured following different treatments by Evans blue dye quantification. Thus, rats were submitted to Von Frey and Formalin tests in orofacial region before and after pharmacological inhibition of the CSE-H2S system combined or not with CFA-induced TMJ inflammation. Pretreatment with CSE inhibitor, propargylglycine (PAG; 88.4 μmol/kg) reduced temporomandibular inflammatory pain when injected locally as well as systemically. In particular, local PAG injection seems to be more effective for hypernociceptive responses in orofacial persistent inflammation since its action is evidenced in the majority analyzed periods of the inflammatory process compared to its systemic use. Moreover, local injection seems to act on temporomandibular vascular permeability, evidenced by decreased plasmatic extravasation induced by local PAG administration. Our data are consistent with the notion that the endogenous synthetized gas H2S modulates persistent orofacial pain responses revealing the pharmacological importance of the CSE inhibitor as a possible therapeutic target for their control.

Studies have used paradigms based on animal models to understand human emotional behavior because they appear to be correlated with fear- and anxiety-related defensive patterns in non-human mammals. In this context, tonic immobility (TI) behavior is an innate response associated with extreme threat situations, such as predator attack. Some reports have demonstrated the involvement of corticotropin-releasing factor (CRF) in regulation of the endocrine system, defensive behaviors and behavioral responses to stress. Particularly, a previous study showed that the activation of CRF receptors in the basolateral (BLA) or central (CeA) nuclei of the amygdala increased TI responses, whereas treatment with a non-selective CRF antagonist, alpha-helical-CRF

Psychological stress is an important perpetuating, worsening and risk factor for temporomandibular disorders of muscular or articular origin. Occlusion instability, by the way, is considered a risk factor of this pathology and can be reproduced in some experimental animal models. The exact physiologic mechanism underlying these relations however, remains unclear. Our purpose was to test the hypothesis that chronic stress and unilateral exodontia induce metabolic and vascular changes in the medial pterygoid muscle of rats. Adult Wistar rats were submitted to chronic unpredictable stress and/or unilateral exodontia and their plasma and medial pterygoid muscle were removed for analysis. The parameters evaluated included plasma levels of corticosterone, metabolic activity by succinate dehydrogenase, oxidative capacity by nicotinamide adenine dinucleotide diaphorase, capillary density by laminin and alfa-CD staining and reactive oxidative species production. Chronic unpredictable stress as an isolated factor, increased oxidative metabolism, capillary density and reactive oxygen species production at medial pterygoid muscle. Conversely, exodontia has a main effect in metabolism, promoting glycolytic transformation of muscle fibers. Association of both factors induced a major glycolytic pattern in muscle and vascular changes. Our findings provide insights into the mechanisms, possibly inducing metabolic and vascular alterations on medial pterygoid muscle of rats, by which chronic stress and occlusal instabilities might be involved as risk factors in the pathophysiology of temporomandibular disorders with muscular components.

Aim Although periaqueductal grey matter activation is known to elicit respiratory and cardiovascular responses, the role of this midbrain area in the compensatory responses to hypoxia is still unknown. To test the participation of the periaqueductal grey matter in cardiorespiratory and thermal responses to hypoxia in adult male Wistar rats, we performed a chemical lesion of the dorsolateral/dorsomedial or the ventrolateral/lateral periaqueductal grey matter using ibotenic acid. Methods Pulmonary ventilation, mean arterial pressure, heart rate and body temperature were measured in unanaesthetized rats during normoxic and hypoxic exposure (5, 15, 30 min, 7% O2). Results An ibotenic acid lesion of the dorsolateral/dorsomedial periaqueductal grey matter caused a higher increase in pulmonary ventilation (67.1%, 1730 ± 282.5 mL kg−1 min−1) compared to the Sham group (991.4 ± 194 mL kg−1 min−1) after 15 min in hypoxia, whereas for the ventrolateral/Lateral periaqueductal grey matter lesion, no differences were observed between groups. Mean arterial pressure, heart rate and body temperature were not affected by a dorsolateral/dorsomedial or ventrolateral/lateral periaqueductal grey matter lesion. Conclusion Middle to caudal portions of the dorsolateral/dorsomedial periaqueductal grey matter neurones modulate the hypoxic ventilatory response, exerting an inhibitory modulation during low O2 situations. In addition, the middle to caudal portions of the dorsolateral/dorsomedial or ventrolateral/lateral periaqueductal grey matter do not appear to exert a tonic role on cardiovascular or thermal parameters during normoxic and hypoxic conditions.

Temporomandibular disorder (TMD) is prevalent in dental clinics and can involve problems with the masticatory muscles or the temporomandibular joints (TMJ). The pain of TMD is frequently associated with inflammation in the TMJs, but it's etiology is considered to be multifactorial and includes biologic, behavioral, environmental, social, emotional and cognitive factors. The purpose of this investigation was to evaluate the anxiety-like behavior in rats exposed to temporomandibular inflammation via injection of Freund's Adjuvant (CFA) with the elevated plus maze (EPM) and light/dark box (LDB) tests and to evaluate nociceptive behavior with the von Frey test at different periods. Moreover, this study measured TMJ inflammation using plasma extravasation (Evans blue test) and the intraarticular infiltration of polymorphonuclear neutrophils (myeloperoxidase quantification). The results showed that rats that were submitted to TMJ inflammation exhibited a decreased number of entries into the open arms of the EPM and a decrease in the time spent in the light compartment and in the number of transitions in the LDB. Additionally, the number of entries in closed arms in the EPM, used as indicator of locomotor activity, did not alter between treatments. Furthermore, increases in mechanical sensitivity and increases in plasma extravasation in the joint tissue occurred throughout the inflammation process, along with an increase in myeloperoxidase in the synovial fluid of TMJ. Our results suggest that the temporomandibular inflammation induced by CFA produced anxiety-like behaviors in rats and induced nociceptive behavior across different periods of inflammation.

This study evaluated whether the administration of a NSAID, sodium diclofenac, can promote alterations in the expression of Fos protein in central amygdala (CEA) and the lateral hypothalamus (LH) after 6 h of experimental tooth movement with a controlled force of 70 g, applied to the superior central incisors of rats. Adult male rats were anesthetized and divided into four groups: Control, no orthodontic appliance (OA); OA activated with 70 g; OA activated with 70 g and pretreated with diclofenac sodium (5 mg/kg, intramuscular); and diclofenac sodium alone. Six hours after the onset of the experiment the rats were reanesthetized and perfused with 4% paraformaldehyde. The brains were removed and fixed, and sections containing the CEA and LH were processed for Fos protein immunohistochemistry. The results show that in the control group, intramuscular injection of a ketamine/xylazine mixture did not induce IR-Fos cells in the CEA or LH. However, in the 70 g group, IR-Fos was the strongest observed (P

Women with temporomandibular disorders (TMD) frequently report pain areas in body regions. This process is associated with central sensitization phenomena, present in chronic pain. The low-level laser therapy (LLLT) has been reported as a therapeutic option for the painful TMD treatment. The aim of this study was to analyze the effect of LLLT on pain intensity (visual analogue scale, VAS), pain sensitivity in orofacial and corporal points (pressure pain threshold, PPT), and on Short Form-McGill Pain Questionnaire (SF-MPQ) indexes of women with myofascial pain (subtype of muscle TMD). Ninety-one women (18-60 years) were included in the study, among which 61 were diagnosed with myofascial pain (Research Diagnostic Criteria for Temporomandibular Disorder-Ia and Ib) and were divided into laser (n = 31) and placebo group (n = 30), and 30 were controls. The LLLT was applied at pre-established points, twice a week, eight sessions (780 nm; masseter and anterior temporal = 5 J/cm2, 20 mW, 10 s; TMJ area = 7.5 J/cm2, 30 mW, 10 s). Pain intensity, pain sensitivity, and the SF-MPQ indexes were measured at the baseline, during laser sessions, and 30 days after treatment. For intra-group comparisons, the Friedman test was performed, and for inter-group, the Mann-Whitney test. Increased pain sensitivity was found in women with myofascial pain when compared to controls (p 0.05). Active laser and placebo reduced the indexes of sensory, total pain, and VAS, maintaining the results after 30 days; there was a reduction in the affective pain rating index for both groups, with no maintenance after 30 days for placebo, and the present pain intensity decreased in the laser group and did not change in the placebo after LLLT. In conclusion, the LLLT active or placebo are effective in reducing the overall subjective perception of myofascial pain (VAS and SF-MPQ indexes); however, they have no effectiveness in reducing the pain sensitivity in orofacial and corporal points (PPT increase).

Corticotropin-releasing factor (CRF) is a peptide that is released from the hypothalamus into widespread areas of the brain. Evidence has suggested that CRF is involved as a neuromodulator outside of the hypothalamic-pituitary-adrenal axis, playing an important role in fear, anxiety, depression and pain modulation. Our previous report demonstrated that CRF receptor activation in basolateral (BLA) or central nuclei of the amygdala (CeA) produces innate fear in guinea pigs. Inhibition of these receptors via administration of α-helical CRF9-41 (a nonspecific antagonist) into the CeA or BLA decreased innate fear behavior [1]. Additionally, there is strong evidence that emotional behavior and nociception can be modulated simultaneously. The present study was conducted to investigate the involvement of the CRF receptors of the BLA or CeA in nociception in guinea pigs. Guinea pigs were treated with CRF and α-helical CRF>9-41> in three different doses or injected with α-helical CRF9-41 preceded by CRF into the BLA or CeA, and they were evaluated using the hot plate test. Our findings indicated that activation of CRF receptors in the BLA and in the CeA promoted antinociception, and this effect was reversed by preadministration of α-helical CRF9-41 in the same area. The treatment with α-helical CRF>9-41> per se into the BLA and CeA did not alter nociception. Thus, nociception modulation occurs in a phasic manner, whereas defensive behavior can occur tonically because the α-helical CRF9-41 did not cause any modification on the index of analgesia in the hot plate test but did reduce innate fear behavior [1].

Hydrogen sulfide (H

Photobiomodulation (PBM) is a therapy induced by a specific type of laser that affects biologic systems through non-thermal ways. The study of its basic mechanism has gained interest since little is known about the causes of the different effects of this treatment. In the present study, we investigated the action of the PBM application rate changes in the peri-implant tissues in rats subjected to tooth movement in different periods. Wistar rats (±250 g) received an apparatus in the region of the central incisors superiors tightly (70 g) or not, and they were also subjected to one or three PBM sessions. After 7 or 14 days, the rats were subjected to euthanasia and the jaws were dissected and processed for histology. For analysis, serial sections were made that were stained by Picrosirius Red for analysis of collagen fibers, Masson’s trichrome for newly formed bone scan, and Hematoxylin-Eosin for quantification of osteoblasts. PBM applied in one or three sessions increased the population of osteoblasts. Still, the application of three sessions of PBM increased the density of collagen fibers and new bone formation compared to the controls. An increase was observed in the interincisal distance in irradiated groups with three PBM sessions and the application of force for both 7 or 14 days. These findings suggest that PBM can contribute positively to the orthodontic movement. So the laser therapy can be used as an adjunct procedure to be performed concurrently for orthodontic treatment in the dental clinic.

Temporomandibular disorder (TMD) has a high prevalence in our society, characterized by a severe pain condition of the masticatory muscles and temporomandibular joint. Despite the indication of multiple factor initiators of TMD, there is still controversy about its etiology and its pathophysiology is poorly understood. Using rats as experimental animals we investigated the effect of unpredictable chronic stress with or without unilateral molar extraction on the contralateral medial pterygoid muscle. Our hypothesis is that these two factors induce changes in morphology, oxidative metabolism and oxidative stress of muscle fibers. Young adult male Wistar rats (±200g) were divided into four groups: a group with extraction and unpredictable chronic stress (E+US); with extraction and without stress (E+C); without extraction and with unpredictable chronic stress (NO+US); and a control group without either extraction or stress (NO+C). The animals were subjected to unilateral extraction of the upper left molars, under intraperitoneal anesthesia with 4% Xylazine (10mg/kg) and 10% Ketamine (80mg/kg) on day zero. The rats of groups E+US and NO+US were submitted to different protocols of stress, from the 14th day after the extraction. The protocols were different every day for five consecutive days, which were repeated from the 6th day for five days more. Contralateral medial pterygoid muscles were obtained on the 24th day after the start of the experiment for morphological, metabolic, capillary density, and oxidative stress analysis. The data from capillary density showed a decrease of capillaries in animals subjected to dental extraction, compared with those without extraction and an increase of laminin expression in the group submitted to the unpredictable chronic stress when compared to the unexposed to stress. SDH test revealed a decrease of light fibers in the group submitted to unilateral extraction of molars, compared with this area in the control group. In E+US and NO+US groups, the deeply stained fibers increased compared to NO+C.·The exodontia factor was able to increase the ROS activity in muscle, whereas the stress factor does not significantly alter ROS in this tissue. It was concluded that both unpredictable chronic stress and the extraction induce metabolic and density of capillary changes in the contralateral medial pterygoid muscle to extraction, suggesting that these factors for a longer period of this experiment could induce muscle damage related to TMD.

Heme oxygenase–carbon monoxide–cGMP (HO–CO–cGMP) pathway has been reported to be involved in peripheral and spinal modulation of inflammatory pain. However, the involvement of this pathway in the modulation of acute painful stimulus in the absence of inflammation remains unknown. Thus, we evaluated the involvement of the HO–CO–cGMP pathway in nociception by means the of analgesia index (AI) in the tail flick test. Rats underwent surgery for implantation of unilateral guide cannula directed toward the lateral ventricle and after the recovery period (5–7 days) were subjected to the measures of baseline tail flick test. Animals were divided into groups to assess the effect of intracerebroventricular administration (i.c.v.) of the following compounds: ZnDPBG (HO inhibitor) or vehicle (Na2CO3), heme-lysinate (substrate overload) or vehicle ( l -lysine), or the selective inhibitor of soluble guanilate cyclase ODQ or vehicle (DMSO 1%) following the administration of heme-lysinate or vehicle. Heme overload increased AI, indicating an antinociceptive role of the pathway. This response was attenuated by i.c.v. pretreatment with the HO inhibitor ZnDPBG. In addition, this effect was dependent on cGMP activity, since the pretreatment with ODQ blocked the increase in the AI. Because CO produces most of its actions via cGMP, these data strongly imply that CO is the HO product involved in the antinociceptive response. This modulation seems to be phasic rather than tonic, since i.c.v. treatment with ZnDPBG or ODQ did not alter the AI. Therefore, we provide evidence consistent with the notion that HO–CO–cGMP pathway plays a key phasic antinociceptive role modulating noninflammatory acute pain.

Tonic immobility behavior (TI) is an innate response characterized by profound motor inhibition that is exhibited by prey when physical contact with a predator is prolonged and the situation inescapable. The periaqueductal gray matter (PAG) is intimately associated with the somatic and autonomic components of defensive reactions. This study investigated whether the TI response was able to recruit specific functional columns of the PAG by examining c-fos immunolocalization in guinea pigs. In the TI group, the innate response was invoked in animals through inversion and physical contention for at least 15 min. In the control group, the animals were physically manipulated only. Our results demonstrate that the defensive behavior of TI is capable of promoting the expression of Fos protein in different areas of the PAG, with higher levels of staining in the ventrolateral (vl) and lateral (l) columns. In addition, our results demonstrate increased Fos immunoreactivity (FOS-IR) in the dorsal raphe nucleus, the Edinger-Westphal nucleus, the cuneiform nucleus and the superior colliculus. In contrast, there were no significant alterations in the number of FOS-IR cells in the inferior colliculus or the oculomotor nucleus. Analysis of the results suggests that neuronal activation after the TI response differs by functional column of the PAG.

The tonic immobility (TI) response is an innate fear behavior associated with intensely dangerous situations, exhibited by many species of invertebrate and vertebrate animals. In humans, it is possible that TI predicts the severity of posttraumatic stress disorder symptoms. This behavioral response is initiated and sustained by the stimulation of various groups of neurons distributed in the telencephalon, diencephalon and brainstem. Previous research has found the highest Fos-IR in the posteroventral part of the medial nucleus of the amygdala (MEA) during TI behavior; however, the neurotransmission of this amygdaloid region involved in the modulation of this innate fear behavior still needs to be clarified. Considering that a major drug class used for the treatment of psychopathology is based on serotonin (5-HT) neurotransmission, we investigated the effects of serotonergic receptor activation in the MEA on the duration of TI. The results indicate that the activation of the 5HT1A receptors or the blocking of the 5HT2 receptors of the MEA can promote a reduction in fear and/or anxiety, consequently decreasing TI duration in guinea pigs. In contrast, blocking the 5HT1A receptors or activating the 5HT2 receptors in this amygdalar region increased the TI duration, suggesting an increase in fear and/or anxiety. These alterations do not appear to be due to a modification of spontaneous motor activity, which might non-specifically affect TI duration. Thus, these results suggest a distinct role of the 5HT receptors in the MEA in innate fear modulation.

The heme oxygenase-carbon monoxide pathway has been shown to play an important role in many physiological processes and is capable of altering nociception modulation in the nervous system by stimulating soluble guanylate cyclase (sGC). In the central nervous system, the locus coeruleus (LC) is known to be a region that expresses the heme oxygenase enzyme (HO), which catalyzes the metabolism of heme to carbon monoxide (CO). Additionally, several lines of evidence have suggested that the LC can be involved in the modulation of emotional states such as fear and anxiety. The purpose of this investigation was to evaluate the activation of the heme oxygenase-carbon monoxide pathway in the LC in the modulation of anxiety by using the elevated plus maze test (EPM) and light-dark box test (LDB) in rats. Experiments were performed on adult male Wistar rats weighing 250-300 g (n=182). The results showed that the intra-LC microinjection of heme-lysinate (600 nmol), a substrate for the enzyme HO, increased the number of entries into the open arms and the percentage of time spent in open arms in the elevated plus maze test, indicating a decrease in anxiety. Additionally, in the LDB test, intra-LC administration of heme-lysinate promoted an increase on time spent in the light compartment of the box. The intracerebroventricular microinjection of guanylate cyclase, an sGC inhibitor followed by the intra-LC microinjection of the heme-lysinate blocked the anxiolytic-like reaction on the EPM test and LDB test. It can therefore be concluded that CO in the LC produced by the HO pathway and acting via cGMP plays an anxiolytic-like role in the LC of rats.

Tonic immobility (TI), also known as death feigning or animal hypnosis, is a reversible state of motor inhibition that is not only triggered by postural inversion and/or movement restraining maneuvers but also by repetitive stimulation and pressure on body parts. Evidence has demonstrated that the basolateral nucleus of the amygdala (BLA) is particularly associated with defensive behavior that involves the emotional states of fear and anxiety. In addition, some reports have demonstrated that serotonin (5-HT) released in the amygdala is increased during states of stress and anxiety, principally in the BLA. In the present study, we investigated the effects of serotonergic activation of the BLA on the duration of TI. The results showed that the microinjection of 5-HT (3.0 microg) into the BLA decreased the duration of TI. Similarly, the administration of a 5-HT1A agonist (0.1 microg of 8-hydroxy-dipropylaminotretalin) or 5-HT2 agonist (0.1 microg of alpha-methyl-5-HT) into the BLA reduced the TI duration. The effect of 5-HT2 agonist was reversed by pretreatment with a dose that had no effect per se (0.01 microg) of ketanserin (5-HT2 receptor antagonists) into the BLA. Moreover, the activation of 5-HT1A and 5-HT2 receptors in the BLA did not alter the spontaneous motor activity in the open field test. The results of the present study indicate that the serotonergic system of the BLA possibly produces a reduction in fear and/or anxiety that reduces the TI duration in guinea pigs, but this is not due to increased spontaneous motor activity induced by serotonergic activation, which might affect TI duration non-specifically.