Persistent monoarthritis of the temporomandibular joint region enhances nocifensive behavior and lumbar spinal Fos expression after noxious stimulation to the hindpaw in rats

Effects of persistent temporomandibular joint (TMJ) inflammation on nociceptive responses of remote bodily areas of the rat were investigated. Monoarthritis of the TMJ region was evoked by the injection of complete Freund’s adjuvant (CFA) into the left TMJ region. Rats without injection of CFA into the TMJ region served as controls (non-CFA group). Time spent on licking behavior evoked by the injection of formalin into the left hindpaw and withdrawal thresholds of mechanical stimulation to both sides of the hindpaw were measured during TMJ inflammation for 3 weeks. Furthermore, expression of Fos protein in the lumbar dorsal horn was immunohistochemically investigated following the injection of formalin into the hindpaw during TMJ inflammation. Formalin-evoked nocifensive behavioral activities were significantly enhanced at 10 and 14 days after CFA injection in the late phase, while the withdrawal threshold to mechanical stimulation was significantly decreased bilaterally at 8, 10 and 14 days after CFA injection. Both formalin-evoked licking behavior and mechanical withdrawal thresholds to bilateral hindpaw at 21 days after CFA injection were similar to those in the non-CFA group. The number of Fos-positive neurons in the lumbar dorsal horn ipsilateral to the formalin injection at 1 and 7 days after CFA injection into the TMJ were similar to those in the non-CFA group; however, those were significantly increased in the laminae I–II and V–VI of the lumbar dorsal horn at 14 days after CFA injection. TMJ inflammation for 7 and 14 days alone produced a small number of Fos-expressing neurons in the lumbar dorsal horn. These results provide evidence that persistent unilateral inflammation of the TMJ region causes an increase in behavioral hyperalgesia of the hindpaw, which is attributed to the modulation of neural activities, in part, in the lumbar dorsal horn, likely mediated by supraspinal neural mechanisms.     

Contribution of peripheral 5-HT2A or 5-HT3 receptors to Fos expression in the trigeminal spinal nucleus produced by acute injury to the masseter muscle during persistent temporomandibular joint inflammation in rats

We investigated the contribution of peripheral 5-HT2A or 5-HT3 receptors to Fos expression in the trigeminal spinal nucleus (VSP) following acute masseter muscle injury in male rats with or without temporomandibular joint (TMJ) inflammation persisting for 7 days. TMJ inflammation was evoked by an injection of complete Freund’s adjuvant (CFA). Two hours after formalin injection into the masseter muscle produced Fos-like immunoreactivity (Fos-LI) in several regions of the VSP and upper cervical spinal cord (C2), such as ventrolateral (vl) area of the trigeminal subnucleus caudalis (Vc)/subnucleus interpolaris (Vi) transition (vl-Vi/Vc), paratrigeminal nucleus (dPa5), middle portion of the Vc (mid-Vc) and Vc/C2 transition (Vc/C2) regions in both groups. Significant increases in the number of Fos-LI were observed in these areas in CFA group compared with non-CFA group. TMJ inflammation alone did not induce a significant level of Fos-LI in the VSP. In order to assess the effect of antagonizing 5-HT2A or 5-HT3 receptors on formalin-induced Fos-LI, rats were pre-treated with local (masseter muscle) administration of ketanserin or tropisetron (0.01, 0.1 mg/rat) 20 min prior to formalin injection. In CFA group, these antagonists given locally reduced the Fos-LI response in the laminae I–II at the mid-Vc and Vc/C2 regions. These antagonists reduced the Fos-LI response in the dPa5, but not in the vl-Vi/Vc region. The Fos-LI response was not affected by i.v. administration of ketanserin (0.01, 0.1 mg/rat) or tropisetron (0.01 mg/rat). In non-CFA group, these antagonists given locally did not reduce the Fos-LI response. These results suggest that peripheral 5-HT2A and 5-HT3 receptors contribute to nociceptive processing in the masseter muscle in TMJ inflammatory conditions.     

Formalin-induced nociceptive behavior and c-Fos expression in middle-aged female rats

The impact of the estrous cycle on the nociceptive response in middle-aged female rats was assessed using the formalin test and c-Fos immunoreactivity as a marker of neural activation. Young (2-month-old) and middle-aged (11-month-old) rats were examined, dividing the middle-aged rats into two groups based on their estrous cycle: regular 4-day estrous cycle and irregular estrous cycle. The right hind paw was subcutaneously injected with 50 μl of 2% formalin or saline as a control. Behavioral changes were observed for 1 h. Cycling rats were used during proestrus. Middle-aged female rats had a significantly higher score for nociceptive behavior compared to young rats, irrespective of estrous cyclicity, which suggests that aging, not the ability to maintain estrous cyclicity, causes hypersensitivity to the formalin injection. Immunohistochemical analysis found that the brain response to formalin injection was also more sensitive in middle-aged rats than young rats; a significant increase in the number of c-Fos immunoreactive cells was found in the ventral portion of the lateral septum of middle-aged rats injected with formalin compared to young and middle-aged rats injected with saline, irrespective of estrous cyclicity. Based on these results, we conclude that the sensitivity to painful stimuli in middle-aged female rats, which are in a neuroendocrine state similar to pre- and peri-menopausal women, is associated with age and not affected by reproductive ability.     

Blockade of peripheral 5HT3 receptor attenuates the formalin-induced nocifensive behavior in persistent temporomandibular joint inflammation of rat

The role of peripheral 5HT3 receptors in the orofacial nocifensive behavior induced by the injection of formalin into masseter muscle was evaluated. The behavioral activities evoked by the formalin injection exhibited a biphasic response in the rats with or without temporomandibular joint (TMJ) inflammation (CFA group or non-CFA group). The orofacial nocifensive behavioral activity was enhanced after TMJ inflammation. Systemic administration of tropisetron, 5HT3 receptor antagonist, reduced the nocifensive behavioral activities in the late phase of orofacial formalin test in CFA group, but not in non-CFA group. Local administration of tropisetron into the masseter muscle in CFA group, but not in non-CFA group also attenuated the behavioral activities in the late phase. Unexpectedly, low dose of local tropisetron reduced the nocifensive behavioral activities in the early phase of orofacial formalin test in CFA group. These data suggest that induction of TMJ inflammation causes the elevation of the orofacial nocifensive behavioral activities evoked by formalin injection into masseter muscle, and that peripheral 5HT3 receptors may play a critical role in nociception and the transmission of orofacial pain.     

Unilateral intra-perilymphatic infusion of substance P enhances ipsilateral vestibulo-ocular reflex gains in the sinusoidal rotation test

Previous studies have reported localization of substance P (SP) within the inner ear and that SP exists abundantly within vestibular endorgans. While SP's functional role in the inner ear remains unclear, SP can act as a neuromodulator in the CNS and directly influences neuronal excitability. We hypothesized that SP might influence neuronal excitability within the vestibular periphery. The present study used the sinusoidal rotation test to investigate the influence of SP after its local application in the guinea pig unilateral inner ear. A tiny hole was made adjacent to the round window in the right ears of Hartley white guinea pigs that had normal tympanic membranes and Preyer reflexes. An osmotic pump infused SP (10⁻⁴ M, 10⁻³ M, and 10⁻² M), neurokinin-1 (NK-1) receptor antagonist (10⁻³ M) alone, or SP (10⁻³ M) + NK-1 receptor antagonist (10⁻³ M) through this hole, with rotation tests performed before, and 12 h and 24 h after the treatment. Results were used to calculate the vestibulo-ocular reflex (VOR) gains. After administration of 10⁻³ M and 10⁻² M SP, significant increases in the VOR gains were noted at 12 h after treatment, with these gains disappearing by 24 h after treatment. This increase was not observed when there was simultaneous NK-1 receptor antagonist administration. There were also no changes in the VOR gains noted after administration of 10⁻⁴ M SP or the NK-1 receptor antagonist alone. These results indicate the possibility that SP may act on vestibular endorgans as an excitatory factor via the NK-1 receptors.     

TMJ inflammation increases Fos expression in the nucleus raphe magnus induced by subsequent formalin injection of the masseter or hindpaw of rats

The study was designed to examine the effect of persistent temporomandibular joint (TMJ) inflammation on neuronal activation in the descending pain modulatory system in response to noxious stimulus. Formalin was injected into the left masseter muscle or hindpaw of rats 10 days after injection of the left TMJ with saline or complete Freund's adjuvant (CFA). The results showed that 10-day persistent TMJ inflammation (induced by CFA) alone did not induce a significant increase in Fos-like immunoreactive (Fos-LI) neurons in the rostral ventromedial medulla (RVM) or locus coeruleus (LC), but that formalin injection of the masseter muscle or hindpaw induced a significant increase in Fos-LI neurons in the RVM and LC of rats with and without TMJ inflammation (P < 0.05). However, persistent TMJ inflammation significantly increased Fos-LI neurons in the nucleus raphe magnus (NRM) induced by subsequent formalin injection of the masseter muscle and hindpaw (70.2% increase and 53.8% increase, respectively, over the control TMJ-saline-injected rats; P < 0.05). The results suggest that persistent TMJ inflammation increases neuronal activity, in particularly in the NRM, by the plastic change of the descending pain modulatory system after ipsilateral application of a noxious stimulus to either orofacial area or a spatially remote body area.     

Using the FT-IR linear dichroism method for molecular order determination of tendon collagen bundles and nylon 6

Polarized Fourier transform-infrared (FT-IR) was used to compare the orientation of vibrational chemical groups of bovine tendon collagen bundles (CBs) to that of nylon 6, a simpler polyamide model, in terms of linear dichroism (LD). Subtraction of spectral profiles identified the most significant differences regarding the amide regions. At 1630 cm⁻¹, the CBs displayed higher peak areas and absorbance when positioned perpendicularly (A_⊥) to the plane of polarized light, in comparison with nylon 6. In contrast, at the 1526 cm⁻¹ amide II spectral region the inverse occurred. In the amide III region (1232 cm⁻¹), the LD was positive and higher for CBs. Dichroic ratios (DR = A_||/A_⊥) calculated from the average of ten measured spectra for CBs and nylon 6 revealed that the values for CBs were <1.0 in the 3298–1655 cm⁻¹ wavenumber range and >1.0 in the 1536–1234 cm⁻¹ wavenumber range. From 1535 to 1120 cm⁻¹, nylon 6 displayed DR values higher than those of CBs. The LD band integrated areas were higher in CBs than in nylon 6. The LD differences between CBs and nylon 6 are probably due to a more complex chemical composition and supramolecular oriented architecture in CBs in comparison to nylon 6.     

Norepinephrine depresses the immunity and disease-resistance ability via α1- and β1-adrenergic receptors of Macrobrachium rosenbergii

In this study, we determined the effects of norepinephrine (NE) on immunity and the pathway of its function in the freshwater giant prawn, Macrobrachium rosenbergii. The total hemocyte count (THC), differential hemocyte count (DHC), phenoloxidase activity, respiratory bursts, superoxide dismutase (SOD) activity, phagocytic activity, and clearance efficiency in response to the pathogen, Lactococcus garvieae, were measured when the freshwater giant prawn, M. rosenbergii (16.2 ± 2.1 g) was individually injected with saline or NE at 0.5, 5.0, and 50.0 pmol prawn⁻¹. Results showed that semi-granular cells, respiratory bursts and phagocytic activity at 2 h, PO activity and clearance efficiency from 2 to 4 h, THC at 8 h, and SOD activity from 4 to 8 h significantly decreased, but hyaline cells at 2 h, and respiratory bursts at 8 h had significantly increased after injection of NE at 50.0 pmol prawn⁻¹. In prawns that had received 5.0 pmol NE prawn⁻¹, the PO activity had decreased at 2 h, SOD activity at 8 h, and the clearance efficiency at 2 h. PO activity had decreased at 2 h after prawns had received 0.5 pmol NE prawn⁻¹. All of the immune parameters had returned to control values by 16 h after receiving NE. However, no significant differences were observed in the granular cells during the experimental period. An injection of NE also significantly increased the mortality of prawns challenged with L. garvieae, which appeared to be dose dependent. In another experiment, NE co-injected with prazosin, metoprolol, or propranolol significantly decreased the mortality of challenged prawns, especially when co-injected with prazosin and metoprolol. These results suggest that stress-inducing NE suppresses the immune system, which in turn promotes the susceptibility of M. rosenbergii to L. garvieae via both α1- and β1-adrenergic receptors.     

Cell proliferation and survival in the vestibular nucleus following bilateral vestibular deafferentation in the adult rat

Cell proliferation and neurogenesis in the brainstem vestibular nucleus complex (VNC) has previously been reported following unilateral vestibular neurectomy in the cat. In this study, we examined the rate of cell proliferation and survival in the adult rat VNC following bilateral vestibular deafferentation (BVD), using injections of bromodeoxyuridine (BrdU) and stereological cell counting. We measured cell proliferation at 24, 48, 72 h and 1 week following BVD and found that it was significantly greater than in sham controls (P = 0.002) and that it varied significantly over time (P = 0.01), peaking at 48 h in the BVD group. Of note was that sham surgery was also associated with an increase in cell proliferation, which changed over time. When we compared the survival of new cells at 1 month after BrdU injection, there was no significant difference in survival between the sham and BVD groups. These results raise questions about the potential functional significance of cell proliferation in the VNC following vestibular lesions.     

Effects of electrolytic lesion of dorsolateral periaqueductal gray on analgesic response of morphine microinjected into the nucleus cuneiformis in rat

The periaqueductal gray (PAG) and nucleus cuneiformis (CnF), like the rostral ventromedial medulla, have functional roles in descending pain-inhibitory pathway related to morphine antinociception. There is not any evidence concerning the role of different regions of the PAG on antinociceptive effect of morphine administered into the CnF in pain modulatory system. In the present study, we investigate whether electrolytic lesion of dorsolateral periaqueductal gray (dl-PAG) influence the analgesic effect of morphine microinjected into the CnF. 71 adult male Wistar rats weighting 230–280 g cannulated bilaterally into the CnF, concurrently lesion of dl-PAG was done. The tail-flick and formalin tests were performed to measure pain and antinociceptive effect of morphine microinjected into the CnF (2.5 μg/0.3 μl saline per side). The tail-flick latency was measured at 15, 30, 45, 60 and 75 min following morphine microinjection. In formalin test, pain behavior was recorded for 60 min in early (0–5 min) and late (15–60 min) phases after formalin injection. Each rat was given a subcutaneous 50-μl injection of formalin 2.5% into plantar surface of hind paw following morphine administration. The results showed that dl-PAG lesion attenuated the effect of morphine microinjected into the CnF both in tail-flick and formalin tests while dl-PAG lesion solely did not alter basal pain behavior as compared to control group. In conclusion, our results suggest the existence of a direct or indirect projection from CnF to the dl-PAG at least at the level of the morphine antinociception in pain modulation.     

Electroactive porous tubular scaffolds with degradability and non-cytotoxicity for neural tissue regeneration

Electroactive degradable porous tubular scaffolds were fabricated from the blends of polycaprolactone and a hyperbranched degradable conducting copolymer at different feed ratios by a solution-casting/salt-leaching method. Scaning electron microscopy (SEM) and microcomputed tomography tests indicated that these scaffolds had homogeneously distributed interconnected pores on the cross-section and surface. The electrical conductivity of films with the same composition as the scaffolds was between 3.4 × 10⁻⁶ and 3.1 × 10⁻⁷ S cm⁻¹, depending on the ratio of hyperbranched degradable conducting copolymer to polycaprolactone. A hydrophilic surface with a contact angle of water about 30° was achieved by doping the films with (±)-10-camphorsulfonic acid. The mechanical properties of the films were investigated by tensile tests, and the morphology of the films was studied by SEM. The scaffolds were subjected to the WST test (a cell proliferation and cytotoxicity assay using water-soluble tetrazolium salts) with HaCaT keratinocyte cells, and the results show that these scaffolds are non-cytotoxic. These degradable electroactive tubular scaffolds are good candidates for neural tissue engineering application.     

Differential effects of background noise of various intensities on neuronal activation associated with arousal and stress response in a maze task

Background noise (BGN) can affect performance of various tasks as a function of its intensity. Such effects may involve modulation of arousal level during task performance, though the neural mechanisms responsible for the intensity-dependence of effects of BGN are still unclear in detail. We examined the effects of BGN (white noise) of various intensities (control, < 40 dB without BGN; 70 dB; 100 dB) during maze task on neuronal activity related to arousal and stress responses using c-Fos immunohistochemistry in rats. Performance (number of errors, time to goal, and number of rearings) during the maze task under 70 dB-BGN, but not 100 dB-BGN, was improved compared with the control condition. In addition, 70 dB-BGN increased c-Fos expression in brain areas responsible for arousal, including mesopontine tegmentum, basal forebrain (BF), locus coeruleus (LC), and cortex, whereas 100 dB-BGN markedly activated neurons in stress-related nuclei, such as the hypothalamic paraventricular nucleus, central nucleus and basolateral nucleus of the amygdala, as well as BF cholinergic neurons, LC neurons, and cortex. These findings suggest that BGN during maze task can induce differential neuronal activation depending on the intensity of BGN in the brain areas relating to arousal and stress responses, which might be involved in maze performance.     

Effects of in vivo injection of anti-chicken CD25 monoclonal antibody on regulatory T cell depletion and CD4+CD25- T cell properties in chickens

Regulatory T cells (Tregs) are defined as CD4⁺CD25⁺ cells in chickens. This study examined the effects of an anti-chicken CD25 monoclonal antibody injection (0.5 mg/bird) on in vivo depletion of Tregs and the properties of CD4⁺CD25⁻ cells in Treg-depleted birds. The CD4⁺CD25⁺ cell percentage in the blood was lower at 8 d post injection than at 0 d. Anti-CD25-mediated CD4⁺CD25⁺ cell depletion in blood was maximum at 12 d post injection. The anti-CD25 antibody injection depleted CD4⁺CD25⁺ cells in the spleen and cecal tonsils, but not in the thymus, at 12 d post antibody injection. CD4⁺CD25⁻ cells from the spleen and cecal tonsils of birds injected with the anti-chicken CD25 antibody had higher proliferation and higher IL-2 and IFNγ mRNA amounts than the controls at 12 d post injection. At 20 d post injection, CD4⁺CD25⁺ cell percentages in the blood, spleen and thymus were comparable to that of the 0 d post injection. It could be concluded that anti-chicken CD25 injection temporarily depleted Treg population and increased and IL-2 and IFNγ mRNA amounts in CD4⁺CD25⁻ cells at 12 d post injection.     

不同应激方式对大鼠下丘脑室旁核c-FoS表达的影响

目的:为了比较大鼠足趾皮下注射福尔马林(formalin)和腹腔注射脂多糖(LPS)诱导下丘脑室旁核(PVN)内c-Fos蛋白表达的差异.方法:本实验采用免疫组织化学ABC双重细胞染色法,观测formalin和LPS应激后下丘脑室旁核大细胞部(mPVN)和小细胞部(pPVN)内c-Fos蛋白和精氨酸加压素(AVP)的定...     

Expression of Fos protein in brainstem after application of l-menthol to the rat nasal mucosa

There are two functional pathways for the nasotrigeminal reflex: the spinal nucleus of trigeminal nerve (SPV) to the Kölliker-Fuse (KF) nucleus and the nucleus of solitary tract (NTS) to the lateral parabrachial nucleus (PBl). Although stimulation of the nasal mucosa by cool temperature induces respiratory depression, it is still unknown whether these nuclei are activated. In the present study, we examined the expression of Fos protein in rat brainstem neurons after nasal application of l-menthol, which is known to activate cold-sensitive nasal receptors. Application of l-menthol, but not paraffin oil, decreased the respiratory rate from 99.7 ± 15.6 to 78.5 ± 7.3 min⁻¹. Furthermore, a significantly higher density of Fos-immunoreactive cells was observed in the SPV and KF in the l-menthol rats than in the controls. In the SPV, the density of Fos-immunoreactive cells was highest at approximately 0.5 mm rostral to the obex in both the l-menthol (48.5 ± 11.5 cells/section) and paraffin oil (26.0 ± 9.6 cells/section) groups. In the KF, the mean density of Fos-immunoreactive cells was highest at approximately 5.0 mm rostral to the obex in both groups (l-menthol: 67.8 ± 14.0 cells/section, control: 41.0 ± 12.7 cells/section). The present study suggests that the SPV-KF pathway is important for the cold-induced respiratory depression.     

Effect of daily linear acceleration training on the hypergravity-induced vomiting response in house musk shrew (Suncus murinus)

The effects of repeated linear acceleration training and the antimotion sickness drug, promethazine, on hypergravity-induced motion sickness were examined in musk shrew (Suncus murinus), which is known to show a vomiting response to motion stimulation. Animals were assigned into five groups: vestibular intact, untreated animals (Sham), vestibular lesioned (VL) animals, vestibular intact animals with promethazine hydrochloride administered as daily drinking water (Prom), vestibular intact animals who underwent horizontal linear accelerator motion training (Train), and vestibular intact animals treated with both promethazine hydrochloride and linear acceleration training (Prom + Train). In Sham animals, the number of vomiting episodes was 14 ± 2 during 2 G exposure for 10 min, and was accompanied by intense Fos expression in the medial vestibular nucleus (MVe), the nucleus of the solitary tract (NTS), the area postrema (AP), and the paraventricular hypothalamic nucleus (PVN). The vomiting response and Fos expression were completely abolished in VL animals, indicating that these responses are mediated via the vestibular system. Although Train and Prom animals experienced a significantly reduced number of hypergravity-induced vomiting episodes compared with Sham animals, the effect was significantly greater in Train animals than in Prom animals. Fos expression in the NTS, AP, and PVN were significantly more reduced in Train animals than in Prom animals. Higher dose of bolus injection of promethazine (50 mg/kg, i.p.) completely abolished the vomiting episodes, although the animals were drowsy and sedated due to side effects. In conclusion, daily linear acceleration training and promethazine could prevent the hypergravity-induced vomiting episodes.     

Exercise-induced energy expenditure: Implications for exercise prescription and obesity

Objective

Walking is commonly recommended to help with weight management. We measured total energy expenditure (TEE) and its components to quantify the impact of increasing exercise-induced energy expenditure (ExEE) on other components of TEE.

Methods

Thirteen obese women underwent an 8-week walking group intervention. TEE was quantified using doubly labeled water, ExEE was quantified using heart rate monitors, daily movement was assessed by accelerometry and resting metabolic rate was measured using indirect calorimetry.

Results

Four of the 13 participants achieved the target of 1500 kcal wk⁻¹ of ExEE and all achieved 1000 kcal wk⁻¹. The average ExEE achieved by the group across the 8 weeks was 1434 ± 237 kcal wk⁻¹. Vigorous physical activity, as assessed by accelerometry, increased during the intervention by an average of 30 min per day. Non-exercise activity thermogenesis (NEAT) decreased, on average, by 175 kcal d⁻¹ (−22%) from baseline to the intervention and baseline fitness was correlated with change in NEAT.

Conclusions

Potential alterations in non-exercise activity should be considered when exercise is prescribed. The provision of appropriate education on how to self-monitor daily activity levels may improve intervention outcomes in groups who are new to exercise.

Practice implications

Strategies to sustain incidental and light physical activity should be offered to help empower individuals as they develop and maintain healthy and long-lasting lifestyle habits.