Low Energy Shock Wave Therapy Inhibits Inflammatory Molecules and Suppresses Prostatic Pain and Hypersensitivity in a Capsaicin Induced Prostatitis Model in Rats.

The effect of low energy shock wave (LESW) therapy on the changes of inflammatory molecules and pain reaction was studied in a capsaicin (10 mM, 0.1 cc) induced prostatitis model in rats. Intraprostatic capsaicin injection induced a pain reaction, including closing of the eyes, hypolocomotion, and tactile allodynia, which effects were ameliorated by LESW treatment. LESW therapy (2Hz, energy flux density of 0.12 mJ/mm2) at 200 and 300 shocks significantly decreased capsaicin-induced inflammatory reactions, reflected by a reduction of tissue edema and inflammatory cells, COX-2 and TNF-α stained positive cells, however, the therapeutic effects were not observed at 100 shocks treated group. Capsaicin-induced IL-1ß, COX-2, IL-6, caspase-1, and NGF upregulation on day 3 and 7, while NALP1 and TNF-α upregulation was observed on day 7. LESW significantly suppressed the expression of IL-1ß, COX-2, caspase-1, NGF on day 3 and IL-1ß, TNF-α, COX-2, NALP1, caspase-1, NGF expression on day 7 in a dose-dependent fashion. LESW has no significant effect on IL-6 expression. Intraprostatic capsaicin injection activates inflammatory molecules and induces prostatic pain and hypersensitivity, which effects were suppressed by LESW. These findings might be the potential mechanisms of LESW therapy for nonbacterial prostatitis in humans.

Mechanical allodynia induced by optogenetic sensory nerve excitation activates dopamine signaling and metabolism in medial nucleus accumbens.

The mesolimbic dopaminergic signaling, such as that originating from the ventral tegmental area (VTA) neurons in the medial part of the nucleus accumbens (mNAc), plays a role in complex sensory and affective components of pain. To date, we have demonstrated that optogenetic sensory nerve stimulation rapidly alters the dopamine (DA) content within the mNAc. However, the physiological role and biochemical processes underlying such rapid and regional dynamics of DA remain unclear. In this study, using imaging mass spectrometry (IMS), we observed that sensitized pain stimulation by optogenetic sensory nerve activation increased DA and 3-Methoxytyramine (3-MT; a post-synaptic metabolite obtained following DA degradation) in the mNAc of the experimental mice. To delineate the mechanism associated with elevation of DA and 3-MT, the de novo synthesized DA in the VTA/substantia nigra terminal areas was evaluated using IMS by visualizing the metabolic conversion of stable isotope-labeled tyrosine (13C15N-Tyr) to DA. Our approach revealed that at steady state, the de novo synthesized DA occupied >10% of the non-labeled DA pool in the NAc within 1.5 h of isotope-labeled Tyr administration, despite no significant increase following pain stimulation. These results suggested that sensitized pain triggered an increase in the release and postsynaptic intake of DA in the mNAc, followed by its degradation, and likely delayed de novo DA synthesis. In conclusion, we demonstrated that short, peripheral nerve excitation with mechanical stimulation accelerates the mNAc-specific DA signaling and metabolism which might be associated with the development of mechanical allodynia.

Pain management using photobiomodulation: Mechanisms, location, and repeatability quantified by pain threshold and neural biomarkers in mice.

Photobiomodulation (PBM) is a simple, efficient and cost-effective treatment for both acute and chronic pain. We previously showed that PBM applied to the mouse head inhibited nociception in the foot. Nevertheless, the optimum parameters, location for irradiation, duration of the effect and the mechanisms of action remain unclear. In the present study, the pain threshold in the right hind paw of mice was studied, after PBM (810 nm CW laser, spot size 1 or 6 cm2 , 1.2-36 J/cm2 ) applied to various anatomical locations. The pain threshold, measured with von Frey filaments, was increased more than 3-fold by PBM to the lower back (dorsal root ganglion, DRG), as well as to other neural structures along the pathway such as the head, neck and ipsilateral (right) paw. On the other hand, application of PBM to the contralateral (left) paw, abdomen and tail had no effect. The optimal effect occurred 2 to 3 hours post-PBM and disappeared by 24 hours. Seven daily irradiations showed no development of tolerance. Type 1 metabotropic glutamate receptors decreased, and prostatic acid phosphatase and tubulin-positive varicosities were increased as shown by immunofluorescence of DRG samples. These findings elucidate the mechanisms of PBM for pain and provide insights for clinical practice.

UVB- and NGF-induced cutaneous sensitization in humans selectively augments cowhage- and histamine-induced pain and evokes mechanical hyperknesis.

Exaggerated itch responses to pruritic chemical provocations and mechanical stimuli are evident in patients with chronic itch, for example, in atopic dermatitis. Currently used human models of itch do not account for such itch sensitization features, and the mechanisms underlying clinical itch sensitization are unknown. This study utilized two established human models of cutaneous nociceptive sensitization to explore how pre-established inflammatory hyperalgesia (ultraviolet-B-irradiation; "UVB") and non-inflammatory neurotrophic pain sensitization (nerve growth factor; "NGF") alter sensitivity to chemical and mechanically evoked itch. Twenty healthy volunteers participated in the UVB experiment. Six volar forearm areas (2 cm diameter) were UVB irradiated with ≤2 × minimal erythemal dose, and two non-irradiated areas were used as controls. Sixteen healthy volunteers participated in the NGF experiment and had 2 µg intradermally injected (4 × 50 µL in 2 cm diameter areas) into both volar forearms. Isotonic saline was applied as control. Pain sensitivity measurements (mechanical and heat pain thresholds) were conducted to validate the models. Subsequently, itch was evoked using histamine and cowhage spicules in the sensitized skin areas, and itch/pain was rated using visual analogue scales. Mechanical hyperknesis (increased itch to punctuate stimuli) was probed with von Frey filaments before/after each itch provocation. Both UVB- and NGF models induced robust primary mechanical hyperalgesia (P < .01) and hyperknesis (P < .05). Neither of the models augmented itch in response to chemical itch provocations but significant increases specifically for pain ratings were observed for both histamine and cowhage (P < .05). This suggests that these models are of limited value as proxies for itch sensitization to pruritogens observed, e.g., in inflammatory dermatoses.

Far-infrared ray patches relieve pain and improve skin sensitivity in myofascial pain syndrome: A double-blind randomized controlled study.

OBJECTIVE: Myofascial pain syndrome (MPS) is a common disorder characterized by muscle pain if myofascial trigger points (MTrP) are stimulated. This study evaluated the effectiveness of far-infrared ray (FIR) patches in reducing the severity of pain in patients with MPS. METHODS: A double-blind, randomized controlled study involving 125 patients with MPS and 201 MTrPs located in the trapezius muscle. A FIR patch was applied to 98 MTrPs for 24h in the intervention group (61 patients) and a placebo patch was applied to 91 MTrPs in the control group (57 patients) at the end. Pain intensity was measured using the visual analogue scale (V) while pressure pain threshold (P) and maximal pain tolerance (T) were measured using an algometer before and after treatment. RESULTS: The mean age of the patients was 37.16 years old and 67% were female. There was a positive correlation between P and T (p<0.001). Older Age was associated with higher P and T due to poor skin sensitivity (p<0.001). V improved significantly in both groups to a similar extent, but only in the intervention group, P and T decreased significantly (which implied better skin sensitivity) (p<0.05). P and T decreased the most in the female group aged over 35, probably due to thinner skin in this subgroup. CONCLUSIONS: FIR and placebo patches were equally effective at relieving pain (with decreased V), but P and T dropped only in the intervention group with FIR patches. This probably resulted from FIR penetrated only to the skin layer and improved skin sensitivity with more blood circulation, but the muscle remained unaffected. Further studies should investigate the effect of longer exposure or higher energy applications.

Antinociceptive effects of low-level laser therapy at 3 and 8 j/cm2 in a rat model of postoperative pain: possible role of endogenous Opioids.

Low-level laser therapy (LLLT) is the direct application of light to stimulate cell responses (photobiomodulation) to promote tissue healing, reduce inflammation, and induce analgesia; the molecular basis for these effects of LLLT remains unclear. The objective of this study was to evaluate the analgesic effect of LLLT in the rat plantar incision model of postoperative pain as well as to investigate some of the possible mechanisms involved in this effect. Wistar rats were submitted to plantar incision and treated with LLLT (830 nm, continuous-mode, 30 mW/cm2 , 1-12 J/cm2 ). Postoperative thermal and mechanical hypersensitivity were monitored for 24 hours post-incision. In addition, the animals were pretreated with saline, naloxone (a nonselective opioid receptor antagonist; 20 µg/5 µl) or methysergide (5-HT2C , 5-HT2A , 5-HT7 , 5-HT5a , 5-HT6, and 5-HT1F receptors antagonist; 30 µg/5 µl). Moreover, 24 hours after incision and treatment, the TNF-α and IL-1ß levels in serum were evaluated. Our results demonstrate, for the first time, that LLLT at 3 or 8 J/cm2 , but not at 1-2, 4-7, or 9-12 J/cm2 , induced an analgesic effect on postoperative pain. Naloxone, but not methysergide, blocked the LLLT-induced anti-nociceptive effect. Additionally, IL-1-ß and TNF-α production significantly decreased after LLLT at 3 or 8 J/cm2 . Our results suggest that LLLT at 3 or 8 J/cm2 primarily modulates the endogenous opioids system and is not directly mediated by serotonergic receptors. Reduction of IL-1ß and TNF-α may play a role in the antinociceptive action of LLLT. Lasers Surg. Med. 49:844-851, 2017. © 2017 Wiley Periodicals, Inc.

The mechanistic basis for photobiomodulation therapy of neuropathic pain by near infrared laser light.

BACKGROUND AND OBJECTIVE: Various irradiances have been reported to be beneficial for the treatment of neuropathic pain with near infrared light. However, the mechanistic basis for the beneficial outcomes may vary based on the level of irradiance or fluence rate used. Using in vivo and in vitro experimental models, this study determined the mechanistic basis of photobiomodulation therapy (PBMT) for the treatment of neuropathic pain using a high irradiance. STUDY DESIGN/MATERIALS AND METHODS: In vitro experiments: Cultured, rat DRG were randomly assigned to control or laser treatment (LT) groups with different irradiation times (2, 5, 30, 60, or 120 seconds). The laser parameters were: output power = 960 mW, irradiance = 300 mW/cm2 , 808 nm wavelength, and spot size = 3 cm diameter/area = 7.07cm2 , with different fluences according to irradiation times. Mitochondrial metabolic activity was measured with the MTS assay. The DRG neurons were immunostained using a primary antibody to ß-Tubulin III. In vivo experiments: spared nerve injury surgery (SNI), an animal model of persistent peripheral neuropathic pain, was used. The injured rats were randomly divided into three groups (n = 5). (i) Control: SNI without LT; (ii) Short term: SNI with LT on day 7 and euthanized on day 7; (iii) Long term: SNI with LT on day 7 and euthanized on day 22. An 808 nm wavelength laser was used for all treatment groups. Treatment was performed once on day 7 post-surgery. The transcutaneous treatment parameters were: output power: 10 W, fluence rate: 270 mW/cm2 , treatment time: 120 seconds. The laser probe was moved along the course of the sciatic/sural nerve during the treatment. Within 1 hour of irradiation, behavior tests were performed to assess its immediate effect on sensory allodynia and hyperalgesia caused by SNI. RESULTS: In vitro experiments: Mitochondrial metabolism was significantly lower compared to controls for all LT groups. Varicosities and undulations formed in neurites of DRG neurons with a cell body diameter 30 µm or less. In neurites of DRG neurons with a cell body diameter of greater than 30 µm, varicosities formed only in the 120 seconds group. In vivo experiments: For heat hyperalgesia, there was a statistically significant reduction in sensitivity to the heat stimulus compared to the measurements done on day 7 prior to LT. A decrease in the sensitivity to the heat stimulus was found in the LT groups compared to the control group on days 15 and 21. For cold allodynia and mechanical hyperalgesia, a significant decrease in sensitivity to cold and pin prick was found within 1 hour after LT. Sensitivity to these stimuli returned to the control levels after 5 days post-LT. No significant difference was found in mechanical allodynia between control and LT groups for all time points examined. CONCLUSION: These in vitro and in vivo studies indicate that treatment with an irradiance/fluence rate at 270 mW/cm2 or higher at the level of the nerve can rapidly block pain transmission. A combination therapy is proposed to treat neuropathic pain with initial high irradiance/fluence rates for fast pain relief, followed by low irradiance/fluence rates for prolonged pain relief by altering chronic inflammation. Lasers Surg. Med. 49:516-524, 2017. © 2017 Wiley Periodicals, Inc.

Long-lasting antinociceptive effects of green light in acute and chronic pain in rats.

Treatments for chronic pain are inadequate, and new options are needed. Nonpharmaceutical approaches are especially attractive with many potential advantages including safety. Light therapy has been suggested to be beneficial in certain medical conditions such as depression, but this approach remains to be explored for modulation of pain. We investigated the effects of light-emitting diodes (LEDs), in the visible spectrum, on acute sensory thresholds in naive rats as well as in experimental neuropathic pain. Rats receiving green LED light (wavelength 525 nm, 8 h/d) showed significantly increased paw withdrawal latency to a noxious thermal stimulus; this antinociceptive effect persisted for 4 days after termination of last exposure without development of tolerance. No apparent side effects were noted and motor performance was not impaired. Despite LED exposure, opaque contact lenses prevented antinociception. Rats fitted with green contact lenses exposed to room light exhibited antinociception arguing for a role of the visual system. Antinociception was not due to stress/anxiety but likely due to increased enkephalins expression in the spinal cord. Naloxone reversed the antinociception, suggesting involvement of central opioid circuits. Rostral ventromedial medulla inactivation prevented expression of light-induced antinociception suggesting engagement of descending inhibition. Green LED exposure also reversed thermal and mechanical hyperalgesia in rats with spinal nerve ligation. Pharmacological and proteomic profiling of dorsal root ganglion neurons from green LED-exposed rats identified changes in calcium channel activity, including a decrease in the N-type (CaV2.2) channel, a primary analgesic target. Thus, green LED therapy may represent a novel, nonpharmacological approach for managing pain.

Red LED photobiomodulation reduces pain hypersensitivity and improves sensorimotor function following mild T10 hemicontusion spinal cord injury.

BACKGROUND: The development of hypersensitivity following spinal cord injury can result in incurable persistent neuropathic pain. Our objective was to examine the effect of red light therapy on the development of hypersensitivity and sensorimotor function, as well as on microglia/macrophage subpopulations following spinal cord injury. METHODS: Wistar rats were treated (or sham treated) daily for 30 min with an LED red (670 nm) light source (35 mW/cm(2)), transcutaneously applied to the dorsal surface, following a mild T10 hemicontusion injury (or sham injury). The development of hypersensitivity was assessed and sensorimotor function established using locomotor recovery and electrophysiology of dorsal column pathways. Immunohistochemistry and TUNEL were performed to examine cellular changes in the spinal cord. RESULTS: We demonstrate that red light penetrates through the entire rat spinal cord and significantly reduces signs of hypersensitivity following a mild T10 hemicontusion spinal cord injury. This is accompanied with improved dorsal column pathway functional integrity and locomotor recovery. The functional improvements were preceded by a significant reduction of dying (TUNEL(+)) cells and activated microglia/macrophages (ED1(+)) in the spinal cord. The remaining activated microglia/macrophages were predominantly of the anti-inflammatory/wound-healing subpopulation (Arginase1(+)ED1(+)) which were expressed early, and up to sevenfold greater than that found in sham-treated animals. CONCLUSIONS: These findings demonstrate that a simple yet inexpensive treatment regime of red light reduces the development of hypersensitivity along with sensorimotor improvements following spinal cord injury and may therefore offer new hope for a currently treatment-resistant pain condition.

Effects of 660- and 980-nm low-level laser therapy on neuropathic pain relief following chronic constriction injury in rat sciatic nerve.

Neuropathic pain (NP) is one of the most suffered conditions in medical disciplines. The role of reactive oxygen species (ROS) and oxidative stress in the induction of NP was studied by many researchers. Neuropathies lead to medical, social, and economic isolation of the patient, so various therapies were used to treat or reduce it. During the recent years, low-level laser therapy (LLLT) has been used in certain areas of medicine and rehabilitation. Chronic constriction injury (CCI) is a well-known model for neuropathic pain studies. In order to find the effects of different wavelengths of LLLT on the injured sciatic nerve, the present research was done. Thirty Wistar adult male rats (230-320 g) were used in this study. The animals were randomly divided into three groups (n = 10). To induce neuropathic pain for the sciatic nerve, the CCI technique was used. Low-level laser of 660 and 980 nm was used for two consecutive weeks. Thermal and mechanical hyperalgesia was done before and after surgery on days 7 and 14, respectively. Paw withdrawal thresholds were also evaluated. CCI decreased the pain threshold, whereas both wavelengths of LLLT for 2 weeks increased mechanical and thermal threshold significantly. A comparison of the mechanical and thermal threshold showed a significant difference between the therapeutic effects of the two groups that received LLLT. Based on our findings, the laser with a 660-nm wavelength had better therapeutic effects than the laser with a 980-nm wavelength, so the former one may be used for clinical application in neuropathic cases; however, it needs more future studies.

Axonal hyperexcitability after combined NGF sensitization and UV-B inflammation in humans.

BACKGROUND: Both nerve growth factor (NGF) and ultraviolet-B (UV-B) irradiation sensitize nociceptive nerve endings and increase axonal excitability of nociceptors. Combining NGF and UV-B treatment is supra-additive for sensory sensitization and even caused spontaneous pain in about 70% of the subjects. METHODS: UV-B irradiation was performed at day 21 after intradermal NGF injection in 13 volunteers. Pain thresholds, electrically induced axon reflex erythema and pain (1.5-fold pain threshold, 5-100 Hz) was analysed at days 22, 24, 28, 35, 49 and 70 and correlated to hyperalgesia and spontaneous pain. RESULTS: Electrical pain threshold after combined NGF/UVB was reduced below single treatment at 24 h but not at 72 h post-UV-B irradiation. At the NGF/UV-B site, electrical pain was enhanced at all frequencies compared with single NGF and UV-B sites at 24 and 72 h with pain ratings exceeding control values about twofold to threefold [65 ± 7 vs. 25 ± 8 visual analogue scale (VAS) (24 h) and 55 ± 9 vs. 22 ± 5 VAS (72 h)]. Hyperalgesia to electrical stimulation correlated with hyperalgesia to pinprick (Spearman r = 0.44; p < 0.001, Bonferroni corr.) and supra-threshold heat (Spearman r = 0.55; p < 0.001) stimulation at 24 h only. Electrical pain thresholds at the NGF/UV-B site weakly correlated to spontaneous pain levels (Spearman r = 0.3; p = 0.025, without Bonferroni correction). In contrast, electrically induced pain or axon reflex erythema did not correlate to spontaneous pain levels. CONCLUSIONS: The combination of NGF and UV-B increases axonal excitability that contributes to hyperalgesia and might also facilitate ongoing spontaneous pain.

Evaluation of low-level laser therapy effectiveness on the pain and masticatory performance of patients with myofascial pain.

This study investigated the effect of low-level laser therapy (LLLT) on the masticatory performance (MP), pressure pain threshold (PPT), and pain intensity in patients with myofascial pain. Twenty-one subjects, with myofascial pain according to Research Diagnostic Criteria/temporomandibular dysfunction, were divided into laser group (n = 12) and placebo group (n = 9) to receive laser therapy (active or placebo) two times per week for 4 weeks. The measured variables were: (1) MP by analysis of the geometric mean diameter (GMD) of the chewed particles using Optocal test material, (2) PPT by a pressure algometer, and (3) pain intensity by the visual analog scale (VAS). Measurements of MP and PPT were obtained at three time points: baseline, at the end of treatment with low-level laser and 30 days after (follow-up). VAS was measured at the same times as above and weekly throughout the laser therapy. The Friedman test was used at a significance level of 5% for data analysis. The study was approved by the Ethics Committee of the Federal University of Sergipe (CAAE: 0025.0.107.000-10). A reduction in the GMD of crushed particles (p < 0.01) and an increase in PPT (p < 0.05) were seen only in the laser group when comparing the baseline and end-of-treatment values. Both groups showed a decrease in pain intensity at the end of treatment. LLLT promoted an improvement in MP and PPT of the masticatory muscles.

Reduction of pain thresholds in fibromyalgia after very low-intensity magnetic stimulation: a double-blinded, randomized placebo-controlled clinical trial.

BACKGROUND: Exposure to electromagnetic fields has been reported to have analgesic and antinociceptive effects in several organisms. OBJECTIVE: To test the effect of very low-intensity transcranial magnetic stimulation on symptoms associated with fibromyalgia syndrome. METHODS: A double-blinded, placebo-controlled clinical trial was performed in the Sagrado Corazón Hospital, Seville, Spain. Female fibromyalgia patients (22 to 50 years of age) were randomly assigned to either a stimulation group or a sham group. The stimulation group (n=28) was stimulated using 8 Hz pulsed magnetic fields of very low intensity, while the sham group (n=26) underwent the same protocol without stimulation. Pressure pain thresholds before and after stimulation were determined using an algometer during the eight consecutive weekly sessions of the trial. In addition, blood serotonin levels were measured and patients completed questionnaires to monitor symptom evolution. RESULTS: A repeated-measures ANOVA indicated statistically significant improvement in the stimulation group compared with the control group with respect to somatosensory pain thresholds, ability to perform daily activities, perceived chronic pain and sleep quality. While improvement in pain thresholds was apparent after the first stimulation session, improvement in the other three measures occurred after the sixth week. No significant between-group differences were observed in scores of depression, fatigue, severity of headaches or serotonin levels. No adverse side effects were reported in any of the patients. CONCLUSIONS: Very low-intensity magnetic stimulation may represent a safe and effective treatment for chronic pain and other symptoms associated with fibromyalgia.

Effect of a single 30 min UMTS mobile phone-like exposure on the thermal pain threshold of young healthy volunteers.

One of the most frequently investigated effects of radiofrequency electromagnetic fields (RF EMFs) on the behavior of complex biological systems is pain sensitivity. Despite the growing body of evidence of EMF-induced changes in pain sensation, there is no currently accepted experimental protocol for such provocation studies for the healthy human population. In the present study, therefore, we tested the effects of third generation Universal Mobile Telecommunications System (UMTS) RF EMF exposure on the thermal pain threshold (TPT) measured on the surface of the fingers of 20 young adult volunteers. The protocol was initially validated with a topical capsaicin treatment. The exposure time was 30 min and the genuine (or sham) signal was applied to the head through a patch antenna, where RF EMF specific absorption rate (SAR) values were controlled and kept constant at a level of 1.75 W/kg. Data were obtained using randomized, placebo-controlled trials in a double-blind manner. Subjective pain ratings were tested blockwise on a visual analogue rating scale (VAS). Compared to the control and sham conditions, the results provide evidence for intact TPT but a reduced desensitization effect between repeated stimulations within the individual blocks of trials, observable only on the contralateral side for the genuine UMTS exposure. Subjective pain perception (VAS) data indicated marginally decreased overall pain ratings in the genuine exposure condition only. The present results provide pioneering information about human pain sensation in relation to RF EMF exposure and thus may contribute to cover the existing gap between safety research and applied biomedical science targeting the potential biological effects of environmental RF EMFs.

Laser therapy and needling in myofascial trigger point deactivation.

The aim of this study was to evaluate different approaches to deactivating myofascial trigger points (MTPs). Twenty-one women with bilateral MTPs in the masseter muscle were randomly divided into three groups: laser therapy, needle treatment and control. Treatment effectiveness was evaluated after four sessions with intervals ranging between 48 and 72 h. Quantitative and qualitative methods were used to measure pain perception/sensation. The Wilcoxon test based on results expressed on a visual analog scale (VAS) demonstrated a significant (P < 0.05) decrease in pain only in the laser and needle treatments groups, although a significant increase in the pressure pain threshold was evident only for needling with anesthetic injection (P = 0.0469), and laser therapy at a dose of 4 J/cm² (P = 0.0156). Based on these results, it was concluded that four sessions of needling with 2% lidocaine injection with intervals between 48 and 72 h without a vasoconstrictor, or laser therapy at a dose of 4 J/cm², are effective for deactivation of MTPs.

The relation between methyl aminolevulinate concentration and inflammation after photodynamic therapy in healthy volunteers.

Inflammation and pain are well known adverse-effects in photodynamic therapy (PDT). There is currently a tendency towards introducing lower concentrations of the photosensitizer than used in the standard treatment for various indications. The aim of this study was to investigate whether reduced concentrations of methyl aminolevulinate (MAL) can reduce inflammation (erythema) during PDT treatment. We measured the formation of protoporphyrin IX (PpIX) using fluorescence and monitored both erythema and pain during and after PDT treatment with conventional 16% MAL and threee reduced concentrations of 2, 0.75, and 0.25% in twenty-four healthy volunteers. We found that lowering the MAL concentration reduced PpIX fluorescence and erythema after PDT treatment. There was a strong correlation (R(2) = 0.70) between the PpIX fluorescence and erythema after treatment. A further increase in erythema after PDT was dependent on pre-treatment skin erythema. PpIX fluorescence could explain 70% of the increase in erythema (P < 0.0005). Pain and post-treatment hyperpigmentation can be reduced but not eliminated by limiting the MAL concentration. An efficacy study of PDT with these three reduced concentrations has not been performed.

Intense focused ultrasound as a potential research tool for the quantification of diurnal inflammatory pain.

Quantifying pain through assay of a human's or animal's response to a known stimulus as a function of time of day is a critical means of advancing chronotherapeutic pain management. Current methods for quantifying pain, even in the context of etiologies involving deep tissue, generally involve stimulation by quantifiable means of either cutaneous (heat-lamp tests, electrical stimuli) or both cutaneous and subcutaneous tissue (von Frey hairs, tourniquets, etc.) or study of proxies for pain (such as stress, via assay of cortisol levels). In this study, we evaluate the usefulness of intense focused ultrasound (iFU), already shown to generate sensations and other biological effects deep to the skin, as a means of quantifying deep diurnal pain using a standard animal model of inflammation. Beginning 5 days after injection of Complete Freund's Adjuvant into the plantar surface of the rat's right hind paw to induce inflammation, the rats were divided into two groups, the light-phase test group (09:00-18:00h) and the dark-phase test group (23:00-06:00h), both of which underwent iFU application deep to the skin. We used two classes of iFU protocol, motivated by the extant literature. One consisted of a single pulse (SP) lasting 0.375s. The other, a multiple pulse (MP) protocol, consisted of multiple iFU pulses each of length 0.075s spaced 0.075s apart. We found the night group's threshold for reliable paw withdrawal to be significantly higher than that of the day group as assayed by each iFU protocol. These results are consistent with the observation that the response to mechanical stimuli by humans and rodents display diurnal variations, as well as the ability of iFU to generate sensations via mechanical stimulation. Since iFU can provide a consistent method to quantify pain from deep, inflamed tissue, it may represent a useful adjunct to those studying diurnal pain associated with deep tissue as well as chronotherapeutics targeting that pain.

Intense focused ultrasound preferentially stimulates subcutaneous and focal neuropathic tissue: preliminary results.

OBJECTIVE: Potential peripheral sources of pain from subcutaneous tissue can require invasive evocative tests for their localization and assessment. Here, we describe studies whose ultimate goal is development of a noninvasive evocative test for subcutaneous, painful tissue. DESIGN: We used a rat model of a focal and subcutaneous neuroma to test the hypothesis that intense focused ultrasound can differentiate focal and subcutaneous neuropathic tissue from control tissue. To do so, we first applied intense focused ultrasound (2 MHz, with individual pulses of 0.1 second in duration) to the rat's neuroma while the rat was under light anesthesia. We started with low values of intensity, which we increased until intense focused ultrasound stimulation caused the rat to reliably flick its paw. We then applied that same intense focused ultrasound protocol to control tissue away from the neuroma and assayed for the rat's response to that stimulation. RESULTS: Intense focused ultrasound of sufficient strength (I(SATA) of 600 +/- 160 W/cm(2) ) applied to the neuroma caused the rat to flick its paw, while the same intense focused ultrasound applied millimeters to a centimeter away failed to induce a paw flick. CONCLUSION: Successful stimulation of the neuroma by intense focused ultrasound required colocalization of the neuroma and intense focused ultrasound supporting our hypothesis.

Effect of frequent laser irradiation on orthodontic pain. A single-blind randomized clinical trial.

OBJECTIVE: To analyze the effect of low-level laser therapy (LLLT) on perception of pain after separator placement and compare it with perceptions of control and placebo groups using a frequent irradiation protocol. MATERIALS AND METHODS: Eighty-eight patients were randomly allocated to a laser group, a light-emitting diode (LED) placebo group, or a control group. Elastomeric separators were placed on the first molars. In the laser and LED groups, first molars were irradiated for 30 seconds every 12 hours for 1 week using a portable device. Pain was marked on a visual analog scale at predetermined intervals. Repeated measure analysis of variance was performed for statistical analysis. RESULTS: The pain scores of the laser group were significantly lower than those of the control group up to 1 day. The pain scores in the LED group were not significantly different from those of the laser group during the first 6 hours. After that point, the pain scores of the LED group were not significantly different from those of the control. CONCLUSIONS: Frequent LLLT decreased the perception of pain to a nonsignificant level throughout the week after separator placement, compared with pain perception in the placebo and control groups. Therefore, LLLT might be an effective method of reducing orthodontic pain.

Local gene expression changes after UV-irradiation of human skin.

UV-irradiation is a well-known translational pain model inducing local inflammation and primary hyperalgesia. The mediators and receptor proteins specifically contributing to mechanical or heat hyperalgesia are still unclear. Therefore, we irradiated buttock skin of humans (n = 16) with 5-fold MED of UV-C and assessed the time course of hyperalgesia and axon reflex erythema. In parallel, we took skin biopsies at 3, 6 and 24 h after UVC irradiation and assessed gene expression levels (RT-PCR ) of neurotrophins (e.g. NGF, BDNF, GDNF), ion channels (e.g. NaV1.7, TRPV1), inflammatory mediators (e.g. CCL-2, CCL-3) and enzymes (e.g. PGES, COX2). Hyperalgesia to mechanical impact (12 m/s) and heat (48 °C) stimuli was significant at 6 h (p<0.05 and p<0.01) and 24 h (p<0.005 and p<0.01) after irradiation. Axon reflex erythema upon mechanical and thermal stimuli was significantly increased 3 h after irradiation and particularly strong at 6 h. A significant modulation of 9 genes was found post UV-C irradiation, including NGF (3, 6, 24 h), TrkA (6, 24 h), artemin, bradykinin-1 receptor, COX-2, CCL-2 and CCL-3 (3 and 6 h each). A significant down-regulation was observed for TRPV1 and iNOS (6, 24 h). Individual one-to-one correlation analysis of hyperalgesia and gene expression revealed that changes of Nav1.7 (SCN9A) mRNA levels at 6 and 24 h correlated to the intensity of mechanical hyperalgesia recorded at 24 h post UV-irradiation (Pearson r: 0.57, p<0.04 and r: 0.82, p<0.001). Expression of COX-2 and mPGES at 6 h correlated to the intensity of heat-induced erythema 24 h post UV (r: 0.57, p<0.05 for COX-2 and r: 0.83, p<0.001 for PGES). The individual correlation analyses of functional readouts (erythema and pain response) with local expression changes provided evidence for a potential role of Nav1.7 in mechanical hyperalgesia.