markdownabstractThis thesis presents a novel anatomy mapping tool named Computer Assisted Surgical Anatomy Mapping (CASAM). It allows researchers to map complex anatomy of multiple specimens and compare their location and course. Renditions such as safe zones or danger zones can be visualized, summarizing complex anatomy into comprehensive images, making anatomy research more Accessible. The web-based version of CASAM is used for Personalized Teaching, giving individual feedback on incision lines drawn during surgical courses. It also provides a platform for future International Collaboration between anatomical wetlabs, standardizing anatomy research. The current algorithms used in CASAM are verified and also ready to map complex 3D Anatomy. Future iterations of CASAM will extend its use to everyday surgical practice and tailor-made surgery.

Whiplash injury can produce pain in the neck, arm, and hand, and has been associated with inflammation. However, the relationship between inflammatory responses and pain symptoms remains unknown, hindering the development of appropriate therapeutics for whiplash symptoms. Two joint loading paradigms were used separately in an established rat model of painful cervical facet joint distraction to apply: (1) gross failure, and (2) subfailure distraction of the facet capsular ligament. Behavioral outcomes were compared to determine whether more severe mechanical loading produces greater pain by measuring mechanical hyperalgesia in the shoulder and forepaws. Inflammatory mediators (glia and cytokines) were quantified in the spinal cord and dorsal root ganglion (DRG) after injury. Subfailure loading produced sustained hyperalgesia in the shoulder and forepaw that was significantly greater (p < 0.042) than sham, while an induced capsule failure produced only transient, yet significant (p < 0.021), mechanical hyperalgesia. The absence of hyperalgesia after ligament failure suggests this type of injury may interrupt nociceptive input from the capsule, which is likely necessary to produce sustained pain symptoms. Glial mRNA was significantly increased (p < 0.043) in the spinal cord after ligament failure, but remained unchanged in the DRG. Cytokine mRNA levels in the spinal cord and DRG were also significantly elevated after facet ligament failure, but not after painful subfailure loading. Findings suggest that different joint loading scenarios produced varied inflammatory responses in the CNS. These data support existing clinical reports suggesting that therapeutic interventions directed at the facet capsule may be effective in treating this painful injury.

While cannabinoid receptor agonists have analgesic activity in chronic pain states, they produce a spectrum of central CB1 receptor‐mediated motor and psychotropic side effects. The actions of endocannabinoids, such as anandamide are terminated by removal from the extracellular space, then subsequent enzymatic degradation by fatty‐acid amide hydrolase (FAAH). In the present study, we compared the effect of a selective FAAH inhibitor, URB597, to that of a pan‐cannabinoid receptor agonist HU210 in rat models of chronic inflammatory and neuropathic pain. Systemic administration of URB597 (0.3 mg kg−1) and HU210 (0.03 mg kg−1) both reduced the mechanical allodynia and thermal hyperalgesia in the CFA model of inflammatory pain. In contrast, HU210, but not URB597, reduced mechanical allodynia in the partial sciatic nerve‐ligation model of neuropathic pain. HU210, but not URB597, produced a reduction in motor performance in unoperated rats. The effects of URB597 in the CFA model were dose dependent and were reduced by coadministration with the cannabinoid CB1 antagonist AM251 (1 mg kg−1), or the CB2 and SR144528 (1 mg kg−1). Coadministration with AM251 plus SR144528 completely reversed the effects of URB597. These findings suggest that the FAAH inhibitor URB597 produces cannabinoid CB1 and CB2 receptor‐mediated analgesia in inflammatory pain states, without causing the undesirable side effects associated with cannabinoid receptor activation.

What We Already Know about This Topic Opiates, including morphine, remain a key component in the management of postsurgical pain; however, perioperative use of opiates is associated with a slower resolution of pain and functional status It is possible that the delayed recovery attendant with the administration of morphine may be attributable to morphine-induced enhancement of neuroinflammation What This Article Tells Us That Is New In a mouse tibia fracture and intramedullary pinning model, injury-induced allodynia and neuroinflammation, in particular microglial activation, were significantly increased by morphine Reduction of microglial activation by an antagonist of the Toll-like receptor 4 attenuated the adverse effects of morphine The data are consistent with the premise that morphine increases nociceptive sensitization, functional impairment, and prolongs recovery; suppression of neuroinflammation, and in particular microglial activation, can mitigate the adverse effects of morphine Background: Emerging evidence suggests that opioid use immediately after surgery and trauma may worsen outcomes. In these studies, the authors aimed to determine whether morphine administered for a clinically relevant time period (7 days) in a tibia fracture orthopedic surgery model had adverse effects on postoperative recovery. Methods: Mice were given morphine twice daily for 7 days after unilateral tibial fracture and intramedullary pin fixation to model orthopedic surgery and limb trauma. Mechanical allodynia, limb-specific weight bearing, gait changes, memory, and anxiety were measured after injury. In addition, spinal cord gene expression changes as well as glial activation were measured. Finally, the authors assessed the effects of a selective Toll-like receptor 4 antagonist, TAK-242, on nociceptive and functional changes after injury. Results: Tibial fracture caused several weeks of mechanical nociceptive sensitization (F(1, 216) = 573.38, P < 0.001, fracture + vehicle vs. sham + vehicle, n = 10 per group), and this change was exacerbated by the perioperative administration of morphine (F(1, 216) = 71.61, P < 0.001, fracture + morphine vs. fracture + vehicle, n = 10 per group). In additional testing, injured limb weight bearing, gait, and object location memory were worse in morphine-treated fracture mice than in untreated fracture mice. Postfracture expression levels of several genes previously associated with opioid-induced hyperalgesia, including brain-derived neurotrophic factor and prodynorphin, were unchanged, but neuroinflammation involving Toll-like receptor 4 receptor–expressing microglia was observed (6.8 ± 1.5 [mean ± SD] cells per high-power field for fracture + vehicle vs. 12 ± 2.8 fracture + morphine, P < 0.001, n = 8 per /group). Treatment with a Toll-like receptor 4 antagonist TAK242 improved nociceptive sensitization for about 2 weeks in morphine-treated fracture mice (F(1, 198) = 73.36, P < 0.001, fracture + morphine + TAK242 vs. fracture + morphine, n = 10 per group). Conclusions: Morphine treatment beginning at the time of injury impairs nociceptive recovery and other outcomes. Measures preventing glial activation through Toll-like receptor 4 signaling may reduce the adverse consequences of postoperative opioid administration.

We tested the relation between pain behavior, theta (4–8 Hz) oscillations in somatosensory cortex and burst firing in thalamic neurons in vivo. Optically-induced thalamic bursts attenuated cortical theta and mechanical allodynia. It is proposed that thalamic bursts are an adaptive response to pain that de-synchronizes cortical theta and decreases sensory salience.

We investigated whether tramadol could suppress both neuropathic and inflammatory pain in mice at the same dose level. We also examined the effects of drugs metabolized by glucuronidase, such as acetaminophen (ACAP), indomethacin, probenecid, and valproate, on the antinociceptive activity of tramadol. The administration of 5.6 or 10 mg/kg tramadol suppressed cuff-induced mechanical allodynia, but 10 mg/kg tramadol did not suppress complete Freund's adjuvant (CFA)-induced mechanical allodynia. Although neither tramadol (10 mg/kg) nor ACAP (100 mg/kg) alone produced an antinociceptive effect, their combination suppressed CFA-induced mechanical allodynia. Moreover, pretreatment naloxone, an opioid receptor antagonist, significantly attenuated the antinociceptive effects induced by the combination of tramadol and ACAP and slowed gastrointestinal transit. Similar to ACAP, the combination of tramadol and probenecid or valproate, which has the potential to inhibit uridine 5'-diphosphate (UDP)-glucuronosyltransferase (UGT), also suppressed the CFA-induced mechanical allodynia and slowed gastrointestinal transit. We concluded that tramadol was more beneficial for the treatment of neuropathic pain than inflammatory pain. Furthermore, the antinociceptive effects of the tramadol and ACAP combination were mediated by the μ-opioid receptor, and were thought to be related, at least in part, to the accumulation of the active metabolite, M1.

We investigated the capacity of intrathecal arachidonyl-2'-chloroethylamide (ACEA), a cannabinoid-1 receptor (CB1R) agonist, to inhibit referred hyperalgesia and increased bladder contractility resulting from acute acrolein-induced cystitis in rats. 24 female rats were divided into 4 groups: 1) intrathecal vehicle/intravesical saline; 2) intrathecal vehicle/intravesical acrolein; 3) intrathecal ACEA/intravesical saline; and 4) intrathecal ACEA/intravesical acrolein. Bladder catheters were placed 4-6 days prior to the experiment. On the day of the experiment, rats were briefly anesthetized with isoflurane to recover the external end of the cystostomy catheter. After recovery from anesthesia, pre-treatment cystometry was performed, and mechanical sensitivity of the hindpaws was determined. Rats were again briefly anesthetized with isoflurane to inject ACEA or vehicle into the intrathecal space between L5-L6. Beginning 10 minutes after intrathecal injection, saline or acrolein was infused into the bladder for 30 minutes. Post-treatment cystometry and mechanical sensitivity testing were performed. Rats were euthanized, and bladders were collected, weighed, and fixed for histology. The intrathecal vehicle/intravesical acrolein group developed mechanical hyperalgesia with post-treatment mechanical sensitivity of 6 ± 0.3 g compared to pretreatment of 14 ± 0.4 g (p < 0.01). Pre- and post-treatment hind paw mechanical sensitivity was statistically similar in rats that received intrathecal ACEA prior to intravesical infusion of acrolein (15 ± 0.2 g and 14 ± 0.4 g, respectively). Acrolein treatment increased basal bladder pressure and maximal voiding pressure and decreased intercontraction interval and voided volume. However, intrathecal ACEA was ineffective in improving acrolein-related urodynamic changes. In addition, bladder histology demonstrated submucosal and muscularis edema that was similar for all acrolein-treated groups, irrespective of ACEA treatment. Intravesical saline had no effect on results of cystometry or mechanical sensitivity of the hind paws, regardless of intrathecal treatment. Intrathecal ACEA prevented referred hyperalgesia associated with acute acrolein-induced cystitis. However, in this experimental model, ACEA did not ameliorate the associated urodynamic changes. These findings suggest that pain arising from cystitis may be inhibited by activation of spinal CB1R but the acute local response of the bladder appeared to be unaffected by stimulation of spinal CB1R.

We have evaluated the possible involvement of d-opioid receptor (DOR) in the development and expression of neuropathic pain. For this purpose, partial ligation of the sciatic nerve was performed in DOR knockout mice and wild-type littermates. The development of mechanical and thermal allodynia, as well as thermal hyperalgesia was evaluated by using the von Frey filament model, the coldplate test and the plantar test, respectively. In wild-type and DOR knockout mice, sciatic nerve injury led to a neuropathic pain syndrome revealed in these nociceptive behavioural tests. However, the development of mechanical and thermal allodynia, and thermal hyperalgesia was significantly enhanced in DOR knockout mice. These results reveal the involvement of DOR in the control of neuropathic pain and suggest a new potential therapeutic use of DOR agonists.

We have evaluated the contribution of differences in second messenger signalling to sex differences in inflammatory pain and its control by sex hormones. In normal male but not female rats, epinephrine‐induced mechanical hyperalgesia was antagonized by inhibitors of protein kinase Cε (PKCε), protein kinase A (PKA) and nitric oxide synthetase (NOS). Similarly, in PKCε knockout mice, a contribution of PKCε to epinephrine‐dependent mechanical hyperalgesia occurred in males only. In contrast, hyperalgesia induced by prostaglandin E2, in both females and males, was dependent on PKA and NO. In both sexes, inhibitors of mitogen‐activated protein kinase/extracellular‐signal related kinase kinase (MEK) inhibited epinephrine hyperalgesia. In gonadectomized females, the second messenger contributions to epinephrine hyperalgesia demonstrated the pattern seen in males. Administration of oestrogen to gonadectomized females fully reconstituted the phenotype of the normal female. These data demonstrate gender differences in PKCε, PKA and NO signalling in epinephrine‐induced hyperalgesia which are oestrogen dependent and appear to be exerted at the level of the β‐adrenergic receptor or the G‐protein to which it is coupled.

We find that female mice display no allodynia 10 months after nerve injury, and pregabalin loses its effectiveness after that delay, and in middle-aged mice.

We developed a custom‐made miniaturized neural stimulation system with a liquid crystal polymer (LCP)‐based electrode array for animal experiments. In order to verify the feasibility of the system, motor cortex stimulation (MCS) was applied on the rat pain model induced by sciatic nerve injury.

Voltage‐gated sodium channels play a fundamental role in determining neuronal excitability. Specifically, voltage‐gated sodium channel subtype NaV1.7 is required for sensing acute and inflammatory somatic pain in mice and humans but its significance in pain originating from the viscera is unknown. Using comparative behavioural models evoking somatic and visceral pain pathways, we identify the requirement for NaV1.7 in regulating somatic (noxious heat pain threshold) but not in visceral pain signalling. These results enable us to better understand the mechanisms underlying the transduction of noxious stimuli from the viscera, suggest that the investigation of pain pathways should be undertaken in a modality‐specific manner and help to direct drug discovery efforts towards novel visceral analgesics.

Voltage-gated calcium channel (Cav)2.2 (N-type calcium channels) are key components in nociceptive transmission pathways. Ziconotide, a state-independent peptide inhibitor of Cav2.2 channels, is efficacious in treating refractory pain but exhibits a narrow therapeutic window and must be administered intrathecally. We have discovered an N-triazole oxindole, (3R)-5-(3-chloro-4-fluorophenyl)-3-methyl-3-(pyrimidin-5-ylmethyl)-1-(1H-1,2,4-triazol-3-yl)-1,3-dihydro-2H-indol-2-one (TROX-1), as a small-molecule, state-dependent blocker of Cav2 channels, and we investigated the therapeutic advantages of this compound for analgesia. TROX-1 preferentially inhibited potassium-triggered calcium influx through recombinant Cav2.2 channels under depolarized conditions (IC50 = 0.27 μM) compared with hyperpolarized conditions (IC50 > 20 μM). In rat dorsal root ganglion (DRG) neurons, TROX-1 inhibited ω-conotoxin GVIA-sensitive calcium currents (Cav2.2 channel currents), with greater potency under depolarized conditions (IC50 = 0.4 μM) than under hyperpolarized conditions (IC50 = 2.6 μM), indicating state-dependent Cav2.2 channel block of native as well as recombinant channels. TROX-1 fully blocked calcium influx mediated by a mixture of Cav2 channels in calcium imaging experiments in rat DRG neurons, indicating additional block of all Cav2 family channels. TROX-1 reversed inflammatory-induced hyperalgesia with maximal effects equivalent to nonsteroidal anti-inflammatory drugs, and it reversed nerve injury-induced allodynia to the same extent as pregabalin and duloxetine. In contrast, no significant reversal of hyperalgesia was observed in Cav2.2 gene-deleted mice. Mild impairment of motor function in the Rotarod test and cardiovascular functions were observed at 20- to 40-fold higher plasma concentrations than required for analgesic activities. TROX-1 demonstrates that an orally available state-dependent Cav2 channel blocker may achieve a therapeutic window suitable for the treatment of chronic pain.

Vincristine, a widely used chemotherapeutic agent, produces painful peripheral neuropathy. The underlying mechanisms are not well understood. In this study, we investigated whether voltage-gated sodium channels are involved in the development of vincristine-induced neuropathy. We established a mouse model in which repeated systemic vincristine treatment results in the development of significant mechanical allodynia. Histological examinations did not reveal major structural changes at proximal sciatic nerve branches or distal toe nerve fascicles at the vincristine dose used in this study. Immunohistochemical studies and in vivo two-photon imaging confirmed that there is no significant change in density or morphology of intra-epidermal nerve terminals throughout the course of vincristine treatment. These observations suggest that nerve degeneration is not a prerequisite of vincristine-induced mechanical allodynia in this model. We also provided the first detailed characterization of tetrodotoxin-sensitive (TTX-S) and resistant (TTX-R) sodium currents in dorsal root ganglion neurons following vincristine treatment. Accompanying the behavioural hyperalgesia phenotype, voltage-clamp recordings of small and medium dorsal root ganglion neurons from vincristine-treated animals revealed a significant upregulation of TTX-S Na+ current in medium but not small neurons. The increase in TTX-S Na+ current density is likely mediated by Nav1.6, because in the absence of Nav1.6 channels, vincristine failed to alter TTX-S Na+ current density in medium dorsal root ganglion neurons and, importantly, mechanical allodynia was significantly attenuated in conditional Nav1.6 knockout mice. Our data show that TTX-S sodium channel Nav1.6 is involved in the functional changes of dorsal root ganglion neurons following vincristine treatment and it contributes to the maintenance of vincristine-induced mechanical allodynia.

Vincristine (VCR) is one of the most widely prescribed medications for treating solid tumors and acute lymphoblastic leukemia (ALL) in children and adults. However, its major dose‐limiting toxicity is peripheral neuropathy that can disrupt curative therapy. Peripheral neuropathy can also persist into adulthood, compromising quality of life of childhood cancer survivors. Reducing VCR‐induced neurotoxicity without compromising its anticancer effects would be ideal. Here, we show that low expression of NHP2L1 is associated with increased sensitivity of primary leukemia cells to VCR, and that concomitant administration of VCR with inhibitors of NHP2L1 increases VCR cytotoxicity in leukemia cells, prolongs survival of ALL xenograft mice, but decreases VCR effects on human‐induced pluripotent stem cell‐derived neurons and mitigates neurotoxicity in mice. These findings offer a strategy for increasing VCR’s antileukemic effects while reducing peripheral neuropathy in patients treated with this widely prescribed medication.

Understanding the mechanisms that drive transition from acute to chronic pain is essential to identify new therapeutic targets. The importance of endogenous resolution pathways acting as a "brake" to prevent development of chronic pain has been largely ignored. We examined the role of IL-10 in resolution of neuropathic pain induced by cisplatin. In search of an underlying mechanism, we studied the effect of cisplatin and IL-10 on spontaneous activity (SA) in DRG neurons. Cisplatin (2 mg/kg daily for 3 days) induced mechanical hypersensitivity that resolved within 3 weeks. In both sexes, resolution of mechanical hypersensitivity was delayed in Il10-/- mice, in WT mice treated intrathecally with neutralizing anti-IL-10 antibody, and in mice with cell-targeted deletion of IL-10R1 on advillin-positive sensory neurons. Electrophysiologically, small to medium-sized DRG neurons from cisplatin-treated mice displayed an increase in the incidence of spontaneous activity. Cisplatin treatment also depolarized the resting membrane potential, and decreased action potential voltage threshold and rheobase, while increasing ongoing activity at -45 mV and the amplitude of depolarizing spontaneous fluctuations (DSFs). In vitro addition of IL-10 (10 ng/ml) reversed the effect of cisplatin on SA and on the DSFs amplitudes, but unexpectedly had little effect on the other electrophysiological parameters affected by cisplatin. Collectively, our findings challenge the prevailing concept that IL-10 resolves pain solely by dampening neuroinflammation and demonstrate in a model of chemotherapy-induced neuropathic pain that endogenous IL-10 prevents transition to chronic pain by binding to IL-10 receptors on sensory neurons to regulate their activity.

UNLABELLED To explore further the role of inflammatory processing on peripheral opioid pharmacology, we examined whether the potency of intraarticular (i.a.) or intrathecal (i.t) morphine in tests of thermal and mechanical nociception changed during the induction of experimental arthritis in the rat. Thermal nociception by i.t. morphine (3, 10, and 50 micrograms) or i.a. morphine (100, 1000, and 3000 micrograms) was assessed by means of a modified Hargreaves box ever) 28 h. Mechanical antinociception was determined for the largest applied doses of morphine using von Frey hairs. Morphine produced dose-dependent thermal antinociception after i.t. or i.a. administration: a 50% increase in maximum antinociceptive thermal response (50% effective dose) was produced by i.t. doses of 9.7 micrograms at the start and 9.1 micrograms at the end of this 28-h observational interval, whereas after i.a. administration, 50% effective dose values were 553 micrograms at the start and 660 micrograms at the end. The largest applied dose of either i.t. or i.a. morphine produced mechanical antinociception. On Day 1, the antinociceptive effect for mechanical nociception (expressed as the area under the curve of the percentage of maximal possible effect values at 0.5, 1, 2, and 4 h) was 68% for i.t. morphine 50 micrograms and 53% for i.a. morphine 3000 micrograms. Neither result differed from the corresponding area under the curve values on Day 2. Naloxone administered either i.t. or i.a. abolished the antinociceptive action of morphine given at the same site. We conclude that, although morphine has a peripheral analgesic site of action in a rat arthritis model, its potency for both i.a. and i.t. routes of administration does not change during the onset of arthritis. IMPLICATIONS In this animal study, we showed that the administration of morphine modulates thermal and mechanical antinociception at central and peripheral sites in inflammatory pain.

UNLABELLED The use of von Frey filaments, originally developed by Maximilian von Frey, has become the cornerstone for assaying mechanical sensitivity in animal models and is widely used for human assessment. While there are certain limitations associated with their use that make comparisons between studies not straightforward at times, such as stimulus duration and testing frequency, von Frey filaments provide a good measurement of mechanosensation. Here we describe the application of von Frey filaments to testing in animal models, specifically with respect to determining changes in sensory thresholds in a pain state using the Dixon up-down method. In a literature survey, we found that up to 75% of reports using this method analyze the data with parametric statistical analysis and of those that used nonparametric analysis, none took into account that mechanical sensation is perceived on a logarithmic scale (Weber's Law) when calculating efficacy. Here we outline a more rigorous analysis for calculating efficacy and ED(50)'s from von Frey data that incorporates Weber's Law. We show that this analysis makes statistical and biological sense and provide a specific example of how this change affects data analysis that brings results from animal models more in line with clinical observations. PERSPECTIVE This focus article argues that analyzing von Frey paw withdrawal threshold data obtained by using the Dixon up-down method without considering Weber's Law is inappropriate. An analysis method that incorporates how mechanical sensation is perceived and how its application brings results from animal models more in line with clinical data is presented.

UNLABELLED Previous work demonstrated that both the opioid antagonist (-)-naloxone and the non-opioid (+)-naloxone inhibit toll-like receptor 4 (TLR4) signaling and reverse neuropathic pain expressed shortly after chronic constriction injury. The present studies reveal that the TLR4 contributes to neuropathic pain in another major model (spinal nerve ligation) and to long established (2-4 months) neuropathic pain, not just to pain shortly after nerve damage. Additionally, analyses of plasma levels of (+)-naloxone after subcutaneous administration indicate that (+)-naloxone has comparable pharmacokinetics to (-)-naloxone with a relatively short half-life. This finding accounts for the rapid onset and short duration of allodynia reversal produced by subcutaneous (+)-naloxone. Given that toll-like receptor 2 (TLR2) has also recently been implicated in neuropathic pain, cell lines transfected with either TLR4 or TLR2, necessary co-signaling molecules, and a reporter gene were used to define whether (+)-naloxone effects could be accounted for by actions at TLR2 in addition to TLR4. (+)-Naloxone inhibited signaling by TLR4 but not TLR2. These studies provide evidence for broad involvement of TLR4 in neuropathic pain, both early after nerve damage and months later. Additional, they provide further support for the TLR4 inhibitor (+)-naloxone as a novel candidate for the treatment of neuropathic pain. PERSPECTIVE These studies demonstrated that (+)-naloxone, a systemically available, blood-brain barrier permeable, small molecule TLR4 inhibitor can reverse neuropathic pain in rats, even months after nerve injury. These findings suggest that (+)-naloxone, or similar compounds, be considered as a candidate novel, first-in-class treatment for neuropathic pain.

UNLABELLED Devices designed for mechanical pain threshold studies are often difficult to implement. The purpose of this study was to investigate a simple tool based on calibrated forceps to induce quantifiable mechanical stimulation in the rat on a linear scale. The most suitable protocol was tested by determining the effects of 3 repetitive measurements on both hind paws, respectively, during long-term (9 days), mid-term (1 day), and short-term (2 hours). Only threshold increase related to weight gain over long-term was observed, suggesting that moderate rat training can be used. The capacity of the device to reveal hyperalgesia was tested in a model of carrageenan-induced inflammation in the hind paw. The hyperalgesia was maximal 6 hours after carrageenan injection and progressively decreased. Similar, although more variable, responses were observed with von Frey filaments. Morphine-induced analgesia resulted in a dose-dependent increase of paw threshold. Tolerance to morphine administrated on a once daily schedule (10 mg/kg) during 5 days was revealed by a significant decrease in analgesia by day 3. Taken together, these results demonstrated accuracy of this device for easy, fast, and reproducible measure of mechanical pain threshold on rat limbs. Moreover, it allows the performance of rat testing with minimal constraint, which reduces data variability. PERSPECTIVE The calibrated forceps is an easy to use device well-suited to rapidly test mechanical pain threshold with accuracy. It is well-designed for preclinical behavioral screening of noxious or analgesic properties of molecules.