INFLUENCE OF GROOMING ON PERMANENT ARTHROPOD ASSOCIATES OF BIRDS: CATTLE EGRETS, LICE, AND MITES

Birds have a diverse community of "permanent" arthropods that complete their entire life cycle on the body of the host. Because some of these arthropods are parasites that reduce host fitness, birds control them by grooming, which consists of preening with the beak and scratching with the feet. Although preening is the primary component of grooming, scratching is essential for controlling arthropods on the head and neck, which cannot be preened. Several unrelated groups of birds have evolved comb-like pectinate claws on the middle toenail of each foot. We tested the role of these claws in the control of arthropods by experimentally removing teeth from the claws of captive western cattle egrets (Bubulcus ibis) infested with chewing lice (Insecta: Phthiraptera), feather mites (Acari: Sarcoptiformes), and nasal mites (Acari: Mesostigmata). After a period of 4 mo, we compared the abundance of arthropods on experimental birds to that of control birds with intact teeth. We used video to quantify the grooming rates of the captive birds, which groomed twice as much as wild birds. Experimental and control birds did not differ significantly in grooming time. Both groups virtually eradicated the chewing lice, but not feather mites or nasal mites. We found no support for the hypothesis that pectinate claws increase the efficiency of arthropod control by grooming. Experiments with wild birds are needed to test the hypothesis further under conditions in which birds devote less time to grooming.

EXPERIMENTAL INFECTIONS WITH EUHAPLORCHIS CALIFORNIENSIS AND A SMALL CYATHOCOTYLID INCREASE CONSPICUOUS BEHAVIORS IN CALIFORNIA KILLIFISH (FUNDULUS PARVIPINNIS)

Some parasites manipulate their host's phenotype to enhance predation rates by the next host in the parasite's life cycle. Our understanding of this parasite-increased trophic transmission is often stymied by study-design challenges. A recurring difficulty has been obtaining uninfected hosts with a coevolutionary history with the parasites, and conducting experimental infections that mimic natural processes. In 1996, Lafferty and Morris provided what has become a classic example of parasite-increased trophic transmission; they reported a positive association between the intensity of a brain-infecting trematode (Euhaplorchis californiensis) in naturally infected California killifish (Fundulus parvipinnis) and the frequency of conspicuous behaviors, which was thought to explain the documented 10-30× increase in predation by the final host birds. Here, we address the primary gap in that study by using experimental infections to assess the causality of E. californiensis infection for increased conspicuous behaviors in F. parvipinnis. We hatched and reared uninfected F. parvipinnis from a population co-occurring with E. californiensis, and infected them 1-2 times/week over half their life span with E. californiensis and a small cyathocotylid trematode (SMCY) that targets the host's muscle tissue. At 3 time points throughout the hosts' lives, we quantified several conspicuous behaviors: contorting, darting, scratching, surfacing, and vertical positioning relative to the water's surface. Euhaplorchis californiensis and SMCY infection caused 1.8- and 2.5-fold overall increases in conspicuous behaviors, respectively. Each parasite was also associated with increases in specific conspicuous behaviors, particularly 1.9- and 1.4-fold more darting. These experimental findings help solidify E. californiensis-F. parvipinnis as a classic example of behavioral manipulation. Yet our findings for E. californiensis infection-induced behavioral change were less consistent and strong than those previously documented. We discuss potential explanations for this discrepancy, particularly the idea that behavioral manipulation may be most apparent when fish are actively attacked by predators. Our findings concerning the other studied trematode species, SMCY, highlight that trophically transmitted parasites infecting various host tissues are known to be associated with conspicuous behaviors, reinforcing calls for research examining how communities of trophically transmitted parasites influence host behavior.

Functional roles of neuromedin B and gastrin-releasing peptide in regulating itch and pain in the spinal cord of non-human primates

Despite accumulating evidence in rodents, the functional role of neuromedin B (NMB) in regulating somatosensory systems in primate spinal cord is unknown. We aimed to compare the expression patterns of NMB and its receptor (NMBR) and the behavioral effects of intrathecal (i.t.) NMB with gastrin-releasing peptide (GRP) on itch or pain in non-human primates (NHPs). We used six adult rhesus monkeys. The mRNA or protein expressions of NMB, GRP, and their receptors were evaluated by quantitative reverse transcription polymerase chain reaction, immunohistochemistry, or in situ hybridization. We determined the behavioral effects of NMB or GRP via acute thermal nociception, capsaicin-induced thermal allodynia, and itch scratching response assays. NMB expression levels were greater than those of GRP in the dorsal root ganglia and spinal dorsal horn. Conversely, NMBR expression was significantly lower than GRP receptor (GRPR). I.t. NMB elicited only mild scratching responses, whereas GRP caused robust scratching responses. GRP- and NMB-elicited scratching responses were attenuated by GRPR (RC-3095) and NMBR (PD168368) antagonists, respectively. Moreover, i.t. NMB and GRP did not induce thermal hypersensitivity and GRPR and NMBR antagonists did not affect peripherally elicited thermal allodynia. Consistently, NMBR expression was low in both itch- and pain-responsive neurons in the spinal dorsal horn. Spinal NMB-NMBR system plays a minimal functional role in the neurotransmission of itch and pain in primates. Unlike the functional significance of the GRP-GRPR system in itch, drugs targeting the spinal NMB-NMBR system may not effectively alleviate non-NMBR-mediated itch.

Dynamics and determinants of glucocorticoid metabolite concentrations in wild Verreaux's sifakas

Glucocorticoids have wide-ranging effects on animals' behaviour, but many of these effects remain poorly understood because numerous confounding factors have often been neglected in previous studies. Here, we present data from a 2-year study of 7 groups of wild Verreaux's sifakas (Propithecus verreauxi), in which we examined concentrations of faecal glucocorticoid metabolites (fGCMs, n = 2350 samples) simultaneously in relation to ambient temperatures, food intake, rank, reproduction, adult sex ratios, social interactions, vigilance and self-scratching. Multi-variate analyses revealed that fGCM concentrations were positively correlated with increases in daily temperature fluctuations and tended to decrease with increasing fruit intake. fGCM concentrations increased when males were sexually mature and began to disperse, and dominant males had higher fGCM concentrations than subordinate males. In contrast to males, older females showed a non-significant trend to have lower fGCM levels, potentially reflecting differences in male and female life-history strategies. Reproducing females had the highest fGCM concentrations during late gestation and had higher fGCM levels than non-reproducing females, except during early lactation. Variation in fGCM concentrations was not associated with variation in social interactions, adult sex ratios, vigilance and self-scratching. Altogether, we show that measures of glucocorticoid output constitute appropriate tools for studying energetic burdens of ecological and reproductive challenges. However, they seem to be insufficient indicators for immediate endocrinological responses to social and nonsocial behaviours that are not directly linked to energy metabolism.

Serotonin and noradrenaline modulate chronic itch processing in mice

The roles of serotonin and noradrenaline in the modulation of chronic pruriceptive processing currently remain unclear. To clarify the contribution of serotonin and noradrenaline to chronic itch, the effects of the administration of antidepressants or noradrenaline reuptake inhibitors were evaluated in the present study. A pretreatment with milnacipran, a serotonin and noradrenaline reuptake inhibitor, and mirtazapine, a noradrenergic and specific serotonergic antidepressant, attenuated the induction of spontaneous scratching behavior in mice with chronic itch. The administration of a serotonin reuptake inhibitor, such as fluvoxamine and paroxetine, but not escitalopram, or a noradrenaline reuptake inhibitor, such as atomoxetine and nisoxetine, ameliorated the induction of spontaneous scratching behavior in mice with chronic itch. Furthermore, this attenuation was reversed by the administration of yohimbine, a selective α₂-adrenoceptor antagonist, or methysergide, a non-selective serotonin receptor antagonist. These results suggest that elevated serotonin and noradrenaline levels are involved in the attenuation of scratching behavior induced by chronic itch, and serotonin receptors and an α₂-adrenoceptor play a crucial role in chronic pruriceptive processing.

Pharmacological characteristics of hemokinin-1-derived peptides in rat pruriceptive processing

Hemokinin-1 (HK-1) is a member of mammalian tachykinin peptide family, and [Leu¹¹]-HK-1 has an antagonistic effect on HK-1. The attenuation of pruritogen-induced scratching behavior by pretreatment with [Leu¹¹]-HK-1 indicates the involvement of HK-1 in pruriceptive processing. However, it remains unclear whether the intrathecal or intranasal administration of HK-1-derived peptides, such as [D-Trp^7,9]-[Leu¹¹]-HK-1 or [D-Trp⁷]-[Leu¹¹]-HK-1, elicits the effects different from [Leu¹¹]-HK-1. The induction of scratching by intrathecal administration of HK-1 was attenuated 30 min, 4 h and 24 h after pretreatment with [Leu¹¹]-HK-1, [D-Trp^7,9]-[Leu¹¹]-HK-1 and [D-Trp⁷]-[Leu¹¹]-HK-1 or [D-Trp⁹]-[Leu¹¹]-HK-1, respectively. Similarly, the scratching induced by subcutaneous injection of pruritogens as chloroquine and histamine was ameliorated 30 min and 24 h after pretreatment with [Leu¹¹]-HK-1 and these three HK-1-derived peptides, respectively. Moreover, the effective minimum concentrations of intrathecal administrations of [D-Trp⁹]-[Leu¹¹]-HK-1 on scratching induced by chloroquine and histamine were 10^-6 M, while the effective minimum concentrations of intranasal administration of this peptide on scratching induced by chloroquine and histamine were 10^-5 M and 10^-4 M, respectively. Thus, the present results indicate that the intrathecal administration of HK-1-derived peptides with D-Trp extends its effective time on scratching induced by intrathecal administration of HK-1 and pruritogens such as chloroquine and histamine. Similarly, the induction of scratching by pruritogens was attenuated by intranasal administration of HK-1-derived peptide, although the effective minimum concentration of this peptide was slightly lower than that of intrathecal administration, indicating that intranasal administration is an effective tool for carrying peptides into the brain.

Aimed limb movements in a hemimetabolous insect are intrinsically compensated for allometric wing growth by developmental mechanisms

For aimed limb movements to remain functional, they must be adapted to developmental changes in body morphology and sensory-motor systems. Insects use their limbs to groom the body surface or to dislodge external stimuli, but they face the particular problem of adapting these movements to step-like changes in body morphology during metamorphosis or moulting. Locusts are hemimetabolous insects in which the imaginal moult to adulthood results in a sudden and dramatic allometric growth of the wings relative to the body and the legs. We show that, despite this, hind limb scratches aimed at mechanosensory stimuli on the wings remain targeted to appropriate locations after moulting. In juveniles, the tips of the wings extend less than halfway along the abdomen, but in adults they extend well beyond the posterior end. Kinematic analyses were used to examine the scratching responses of juveniles (fifth instars) and adults to touch of anterior (wing base) and posterior (distal abdomen) targets that develop isometrically, and to wing tip targets that are anterior in juveniles but posterior in adults. Juveniles reach the (anterior) wing tip with the distal tibia of the hind leg using anterior rotation of the thoraco-coxal and coxo-trochanteral (‘hip’) joints and flexion of the femoro-tibial (‘knee’) joint. Adults, however, reach the corresponding (but now posterior) wing tip using posterior rotation of the hip and extension of the knee, reflecting a different underlying motor pattern. This change in kinematics occurs immediately after the adult moult without learning, indicating that the switch is developmentally programmed.

Highlighted Article: A developmentally programmed change in the scratching movements of locusts permits adult animals to aim their movements at new wing tip targets, without learning.

[New findings regarding the neurobiology of pruritus]

Chronic pruritus may arise from different conditions, including dermatological, systemic, neurologic, psychiatric, and psychosomatic diseases, leading to a substantial decrease in the quality of life of affected patients. The neurobiological mechanisms involved in chronic pruritus are not yet fully understood. However, in recent years important achievements have been made in this regard. This article aims to provide an overview of the current understanding of these mechanisms. The complex network of neurons, keratinocytes, inflammatory cells, cytokines, and neurotrophic factors which play a role in the development and maintenance of chronic pruritus are highlighted, as well as the pruritogens involved in pruritic diseases in humans. Additionally, the importance of neuropathy and scratch-induced changes for the pathophysiology of chronic pruritus are discussed. The new findings on the neurobiological mechanisms underlying chronic pruritus have already led to the development of novel therapies, e. g., monoclonal antibodies against specific interleukins, which are important for pruritus transmission. A deeper understanding of the neurobiological mechanisms is necessary in order to develop specifically targeted therapeutic options and thus provide better care for affected patients.

Role of serotonin and noradrenaline in the acute itch processing in mice

The contribution of serotonin and noradrenaline to the modulation of pruriceptive processing was evaluated by administrating antidepressants or noradrenaline reuptake inhibitors. The pretreatment with milnacipran, a serotonin and noradrenaline reuptake inhibitor, and mirtazapine, a noradrenergic and specific serotonergic antidepressant, attenuated the induction of scratching behavior by chloroquine, a representative pruritogen, indicating the involvement of serotonin and/or noradrenaline in the modulation of pruriceptive processing. By contrast, the single administration of noradrenaline reuptake inhibitor such as atomoxetine and nisoxetine or serotonin reuptake inhibitor such as fluvoxamine and escitalopram had little effect on chloroquine-induced scratching, whereas the induction of scratching behavior by chloroquine was significantly ameliorated by co-administration of serotonin reuptake inhibitors and noradrenaline reuptake inhibitors. These results indicate that the simultaneous increases of serotonin and noradrenaline elicit the attenuating effect on pruriceptive processing induced by acute itch, and may also play a crucial role in the descending itch inhibitory system.

Periorbital necrotising fasciitis secondary to scratching

An 80 year-old woman with no relevant medical history, consulted for worsening of right palpebral itching and pain after an insect bite. Her eyelids had areas of laceration due to scratching, which rapidly progressed to fibrinoid necrosis over the first 24hours. Lesions were cultivated, revealing Streptococcus pyogenes and Staphylococcus aureus. The patient was admitted to hospital with the diagnosis of periorbital necrotising fasciitis, in order to receive treatment with intravenous ceftriaxone, linezolid, and immediate surgical debridement. She remained in hospital for 17 days. Daily wound management consisted of debridement of necrotic remains, disinfection with chlorhexidine, and wound dressing with mupirocin, sulfadiazine, and miconazole ointments. The patient suffered streptococcal toxic shock syndrome, but she recovered over the first week. Palpebral reconstruction was performed on day 15, consisting of a preauricular total thickness skin graft for the superior eyelid, and lateral malar advancement to cover the lower eyelid. Adequate cosmetic and functional results were obtained.

Machine-Learning Based Automatic and Real-time Detection of Mouse Scratching Behaviors

Scratching is a main behavioral response accompanied by acute and chronic itch conditions, and has been quantified as an objective correlate to assess itch in studies using laboratory animals. Scratching has been counted mostly by human annotators, which is a time-consuming and laborious process. It has been attempted to develop automated scoring methods using various strategies, but they often require specialized equipment, costly software, or implantation of device which may disturb animal behaviors. To complement limitations of those methods, we have adapted machine learning-based strategy to develop a novel automated and real-time method detecting mouse scratching from experimental movies captured using monochrome cameras such as a webcam. Scratching is identified by characteristic changes in pixels, body position, and body size by frame as well as the size of body. To build a training model, a novel two-step J48 decision tree-inducing algorithm along with a C4.5 post-pruning algorithm was applied to three 30-min video recordings in which a mouse exhibits scratching following an intradermal injection of a pruritogen, and the resultant frames were then used for the next round of training. The trained method exhibited, on average, a sensitivity and specificity of 95.19% and 92.96%, respectively, in a performance test with five new recordings. This result suggests that it can be used as a non-invasive, automated and objective tool to measure mouse scratching from video recordings captured in general experimental settings, permitting rapid and accurate analysis of scratching for preclinical studies and high throughput drug screening.

A comparative study for the isolation of exogenous trace DNA from fingernails

Often fingernails from a victim or suspect involved in a physical assault, such as murder or sexual assault, are submitted to crime laboratories for DNA testing of foreign/exogenous biological material; however, very few studies have been conducted comparing the effectiveness of different sampling methods on the removal of foreign/exogenous DNA while minimizing the fingernail endogenous DNA. In this study three different sampling methods (swabbing, PBS soak, and PrepFiler® lysis buffer soak) were compared in order to identify one that minimizes the amount of endogenous DNA removed and maximizes the amount of foreign/exogenous male DNA removed. The samples were processed using the Tecan HIDEVO150 robot in order to reduce analyst time and the DNA mixtures were interpreted using the probabilistic genotyping software STRmix™. For each sampling method the quantity of male DNA, the mixture proportions, the number of foreign/exogenous male alleles detected, the amount of DNA degradation, and the discrimination power via the likelihood ratio obtained for the foreign/exogenous male DNA donor were determined and compared. The PrepFiler® lysis buffer soak and swabbing sampling methods appear to be equally effective at removing foreign/exogenous DNA from fingernails; however, the lysis buffer soak sampling method extracts more female endogenous DNA from the fingernail and the female DNA is degraded. Marginally higher likelihood ratios were obtained for the swab samples versus the PrepFiler® lysis buffer soak samples; therefore, it was determined that the swabbing sampling method was the best sampling method for the recovery of foreign exogenous DNA from fingernails while minimizing the amount of endogenous DNA removed.

Assessment of rimonabant-like adverse effects of purported CB1R neutral antagonist / CB2R agonist aminoalkylindole derivatives in mice

BACKGROUND

Cannabinoids may be useful in the treatment of CNS disorders including drug abuse and addiction, where both CB1R antagonists / inverse agonists and CB2R agonists have shown preclinical efficacy. TV-5-249 and TV-6-41, two novel aminoalkylindoles with dual action as neutral CB1R antagonists and CB2R agonists, previously attenuated abuse-related effects of ethanol in mice.

PURPOSE

To further characterize these drugs, TV-5-249 and TV-6-41 were compared with the CB1R antagonist / inverse agonist rimonabant in assays relevant to adverse effects and cannabinoid withdrawal.

PROCEDURES AND FINDINGS

The cannabinoid tetrad confirmed that TV-5-249 and TV-6-41 were devoid of CB1R agonist effects at behaviorally-relevant doses, and neither of the novel drugs induced rimonabant-like scratching. Generalized aversive effects were assessed, and rimonabant and TV-5-249 induced taste aversion, but TV-6-41 did not. Schedule-controlled responding and observation of somatic signs were used to assess withdrawal-like effects precipitated by rimonabant or TV-6-41 in mice previously treated with the high-efficacy CB1R agonist JWH-018 or vehicle. Rimonabant and TV-6-41 dose-dependently suppressed response rates in all subjects, but TV-6-41 did so more potently in JWH-018-treated mice than in vehicle-treated mice, while rimonabant equally suppressed responding in both groups. Importantly, rimonabant elicited dramatic withdrawal signs, but TV-6-41 did not.

CONCLUSIONS

These findings suggest differences in both direct adverse effects and withdrawal-related effects elicited by rimonabant, TV-5-249, and TV-6-41, which could relate to neutral CB1R antagonism, CB2R agonism, or a combination of both. Both mechanisms should be explored and exploited in future drug design efforts to develop pharmacotherapies for drug dependence.

Prostaglandin F-2α Stimulates The Secretion of Vascular Endothelial Growth Factor and Induces Cell Proliferation and Migration of Adipose Tissue Derived Mesenchymal Stem Cells

Objective

Tissue engineering today uses factors that can induce differentiation of mesenchymal stem cells (MSCs) into other cell types. However, the problem of angiogenesis in this differentiated tissue remains an unresolved area of research interest. The aim of this study was to investigate the effects of prostaglandin F-2α (PGF-2α) on the expression of vascular endothelial growth factor (VEGF) in human adipose tissue derived MSCs.

Materials and Methods

In this experimental research, human adipose tissue was digested using collagenase. The isolated MSCs cells were treated with PGF-2α (up to 5 μg/ml) and incubated for 96 hours. Cell proliferation, secretion of VEGF and cell migration were spontaneously assayed by MTT, BrdU, ELISA, RT-PCR and scratching methods.

Results

Cell growth at 1.0, 2.5, 5 µg/ml of PGF-2α was not significantly reduced compared to control cells, suggesting that these concentrations of PGF-2α are not toxic to cell growth. The results of the BrdU incorporation assay indicated that, in comparison to untreated cells, BrdU incorporation was respectively 1.08, 1.96, 2.0 and 1.8 fold among cells treated with 0.1, 1.0, 2.5 and 5.0 µg/ml of PGF-2α. The scratching test also demonstrated a positive influence on cell proliferation and migration. Cells treated with 1.0 µg/ml of PGF-2α for 12 hours showed the highest relative migration and coverage in comparison to untreated cells. Quantitative VEGF ELISA and RT- PCR results indicated an increase in VEGF expression and secretion in the presence of PGF-2α. The amount of VEGF produced in response to 0.1, 1.0, 2.5 and 5.0 µg/ml of PGF-2α was 62.4 ± 3.2 , 66.3 ± 3.7, 53.1 ± 2.6 and 49.0 ± 2.3 pg/ml, respectively, compared to the 35.2 ± 2.1 pg/ml produced by untreated cells.

Conclusion

Stimulation of VEGF secretion by PGF-2α treated MSCs could be useful for the induction of angiogenesis in tissue engineering in vitro.

Wearable sensor shown to specifically quantify pruritic behaviors in dogs

Background

Wearable technology is an exciting new field in humans and animals. In dogs activity monitors have helped to provide objective measurement tools where pet owner observation had been the only source of information. Previous research has focused on measuring overall activity versus rest. This has been relatively useful in determining changes in activity in orthopedic disease or post-surgical cases [Malek et al., BMC Vet Res 8:185, 2012, Yashari et al., BMC Vet Res 11:146, 2015]. Assessment of pruritus via changes in activity, however, requires an assumption that increased activity is due to scratching or other pruritic behaviors. This is an inaccurate method with obvious flaws as other behaviors may also register as greater activity. The objective of this study was to validate the ability of a multidimensional high frequency sensor and advanced computer analysis system, (Vetrax®, AgLogica Holdings, Inc., Norcross, GA, USA) to specifically identify pruritic behaviors (scratching and head shaking). To establish differences between behaviors, sensor and time stamped video data were collected from 361 normal and pruritic dogs. Video annotations were made by two observers independently, while blinded to sensor data, and then evaluated for agreement. Annotations that agreed between the two were used for further analysis. The annotations specified behaviors at specific times in order to compare with sensor data. A computer algorithm was developed to interpret and differentiate between these behaviors. Test subject data was then utilized to test and score the system’s ability to accurately predict behaviors.

Results

Results for prediction of head shaking behavior included sensitivity and specificity of 72.16% and 99.78% respectively. Analysis of scratching produced sensitivity and specificity of 76.85% and 99.73% respectively. These results illustrate the ability of the system to accurately report both scratching and head shaking with an overall accuracy of 99.24% and 99.56% respectively.

Conclusions

This study validates the use of this system to accurately and objectively report scratching and head shaking in dogs. While a small portion of scratching or head shaking behaviors may be missed, as indicated by the sensitivity, when detected, the confidence that these behaviors occurred is extremely high. These factors make this system a very useful tool for objective assessment of pruritus in clinical and research settings.

Different perception levels of histamine-induced itch sensation in young adult mice

Itch is an unpleasant sensation that evokes behavioral responses such as scratching the skin. Interestingly, it is conceived that the perception of itch sensation is influenced by age. Indeed, accumulating evidence supports the idea that even children or younger adults show distinctive itch sensation depending on age. This evidence implies the presence of a mechanism that regulates the perception of itch sensation in an age-dependent fashion. Therefore, the purpose of the present study was to investigate a putative mechanism for the age-dependent perception of itch sensation by comparing histamine-induced scratching behaviors in 45-day old (D45) and 75-day old male "young adult" mice. The results indicated that, following histamine administration, the D75 mice spent a longer time scratching than D45 mice. However, the intensity of the calcium influx induced by histamine in primary culture of dorsal root ganglia (DRG) neurons was not different between D45 and D75 mice. Moreover, no apparent difference was observed in mRNA levels of a characteristic His-related receptor and ion channel. In contrast, the mRNA levels of Toll-Like Receptor 4 (TLR4) were increased approximately by two-fold in D75 DRG compared with D45 DRG. Additionally, D75-derived DRG neurons exhibited enhanced intracellular calcium increase by lipopolysaccharide (LPS, a TLR4 agonist) than those of D45 mice. Furthermore, intensities of calcium influx induced by histamine were significantly potentiated when co-treated with LPS in D75 DRG neurons, but not in those of D45 mice. Thus, it appears that D75 mice showed enhanced histamine-induced scratching behaviors not by increased expression levels of histamine-related genes, but probably due to augmented TLR4 expression in DRG neurons. Consequently, the current study found that different perception levels of histamine-induced itch sensation are present in different age groups of young adult mice.

Dissociable effects of the kappa opioid receptor agonist nalfurafine on pain/itch-stimulated and pain/itch-depressed behaviors in male rats

RATIONALE

Nalfurafine is a G protein signaling-biased kappa opioid receptor (KOR) agonist approved in Japan for second-line treatment of uremic pruritus. Neither nalfurafine nor any other KOR agonist is currently approved anywhere for treatment of pain, but recent evidence suggests that G protein signaling-biased KOR agonists may have promise as candidate analgesics/antipruritics with reduced side effects compared to nonbiased or ß-arrestin-signaling-biased KOR agonists.

OBJECTIVES

This study compared nalfurafine effects in rats using assays of pain-stimulated and pain-depressed behavior used previously to evaluate other candidate analgesics. Nalfurafine effects were also examined in complementary assays of itch-stimulated and itch-depressed behavior.

METHODS

Intraperitoneal lactic acid (IP acid) and intradermal serotonin (ID 5HT) served as noxious and pruritic stimuli, respectively, in male Sprague Dawley rats to stimulate stretching (IP acid) or scratching (ID 5HT) or to depress positively reinforced operant responding in an assay of intracranial self-stimulation (ICSS; both stimuli).

RESULTS

Nalfurafine was equipotent to decrease IP acid-stimulated stretching and ID 5HT-stimulated scratching; however, doses of nalfurafine that decreased these pain/itch-stimulated behaviors also decreased control ICSS performance. Moreover, nalfurafine failed to alleviate either IP acid- or ID 5HT-induced depression of ICSS.

CONCLUSIONS

These results suggest that nalfurafine-induced decreases in pain/itch-stimulated behaviors may reflect nonselective decreases in motivated behavior rather than analgesia or antipruritus against the noxious and pruritic stimuli used here. This conclusion agrees with the absence of clinical data for nalfurafine analgesia and the weak clinical data for nalfurafine antipruritus. Nalfurafine bias for G protein signaling may not be sufficient for clinically safe and reliable analgesia or antipruritus.

Syringomyelia and Craniocervical Junction Abnormalities in Chihuahuas

BACKGROUND

Chiari-like malformation (CM) and syringomyelia (SM) are widely reported in Cavalier King Charles Spaniels and Griffon Bruxellois dogs. Increasing evidence indicates that CM and SM also occur in other small and toy breed dogs, such as Chihuahuas.

OBJECTIVES

To describe the presence of SM and craniocervical junction (CCJ) abnormalities in Chihuahuas and to evaluate the possible association of CCJ abnormalities with SM. To describe CM/SM-related clinical signs and neurologic deficits and to investigate the association of CM/SM-related clinical signs with signalment, SM, or CCJ abnormalities.

ANIMALS

Fifty-three client-owned Chihuahuas.

METHODS

Prospective study. Questionnaire analyses and physical and neurologic examinations were obtained before magnetic resonance and computed tomography imaging. Images were evaluated for the presence of SM, CM, and atlantooccipital overlapping. Additionally, medullary kinking, dorsal spinal cord compression, and their sum indices were calculated.

RESULTS

Scratching was the most common CM/SM-related clinical sign and decreased postural reaction the most common neurologic deficit in 73 and 87% of dogs, respectively. Chiari-like malformation and SM were present in 100 and 38% of dogs, respectively. Syringomyelia was associated with the presence of CM/SM-related clinical signs (P = 0.034), and medullary kinking and sum indices were higher in dogs with clinical signs (P = 0.016 and P = 0.007, respectively).

CONCLUSIONS AND CLINICAL IMPORTANCE

Syringomyelia and CCJ abnormalities are prevalent in Chihuahuas. Syringomyelia was an important factor for the presence of CM/SM-related clinical signs, but many dogs suffered from similar clinical signs without being affected by SM, highlighting the clinical importance of CCJ abnormalities in Chihuahuas.

Nanocryl Coating of PMMA Complete Denture Base Materials to Prevent Scratching

The surface of polymethylmethacrylate (PMMA) is vulnerable to indentation by hard objects that may contribute to abrade the material surface and subject it to wear. This phenomenon promotes an increase in the surface roughness leading to microbial colonisation which can endanger the general health of wearers and damage the intra-oral prosthesis. The aim of this study is to investigate the effect of three different nanocryl coating agents (Easy Glaze, G-Coat Plus and Formulation XP) on surface roughness and thickness of PMMA material after a simulating cleaning process utilizing an electric toothbrush and three different dentifrices (pastes and immersion). Acrylic uncoated discs were used as a control group. The results showed that the G-Coat Plus coating agent had less changes in the surface roughness and thickness layer whereas the immersion cleaner revealed less abrasion effect compared with the paste cleaners which could be considered the most suitable cleaner to provide lower abrasivenes and good removal of organic debris. However, using nanofilled sealants did not demonstrate significant improvement in reducing surface roughness p ⟩ 0.05. Nevertheless, it could provide some protection against wearing to the acrylic resin surface during tooth brushing and may provide better resistance to microbial colonisation.

β2-Microglobulin elicits itch-related responses in mice through the direct activation of primary afferent neurons expressing transient receptor potential vanilloid 1

Uremic pruritus is an unpleasant symptom in patients undergoing hemodialysis, and the underlying mechanisms remain unclear. β2-Microglobulin (β2-MG) is well-known as an MHC class I molecule and its level is increased in the plasma of patients undergoing hemodialysis. In this study, we investigated whether β2-MG was a pruritogen in mice. Intradermal injections of β2-MG into the rostral back induced scratching in a dose-dependent manner. Intradermal injection of β2-MG into the cheek also elicited scratching, but not wiping. β2-MG-induced scratching was inhibited by the μ-opioid receptor antagonist naltrexone hydrochloride. β2-MG-induced scratching was not inhibited by antagonists of itch-related receptors (e.g., H₁ histamine receptor (terfenadine), TP thromboxane receptor (DCHCH), BLT1 leukotriene B₄ receptor (CMHVA), and proteinase-activated receptor 2 (FSLLRY-NH₂)). However, β2-MG-induced scratching was attenuated in mice desensitized by repeated application of capsaicin and also by a selective transient receptor potential vanilloid 1 (TRPV1) antagonist (BCTC). In addition, β2-MG induced phosphorylation of extracellular signal-regulated kinase (a marker of activated neurons) in primary culture of dorsal root ganglion neurons that expressed TRPV1. These results suggest that β2-MG is a pruritogen and elicits itch-related responses, at least in part, through TRPV1-expressing primary sensory neurons.

Melanism is related to behavioural lateralization in nestling barn owls

Behavioural laterality is a commonly observed phenomenon in many species suggesting there might be an advantage of using dominantly one side over the other for certain tasks. Indeed, lateralized individuals were often shown to be more successful in cognitive tasks compared to non-lateralized conspecifics. However, stressed individuals are also often, but not always, more strongly lateralized. Because barn owl (Tyto alba) females displaying larger black spots on the tip of their ventral feathers produce offspring that are more resistant to a variety of environmental stressful factors, we examined whether laterality is associated with melanin-based coloration. We recorded whether nestlings use more often the right or left foot to scratch their body and whether they preen more often one side of the body or the other using their bills. We found that the strength of lateralization of preening and scratching was less pronounced in individuals born from heavily spotted mothers. This result might be explained by plumage-related variation in the ability to resist stressful rearing conditions.

Brain mechanism of itch in atopic dermatitis and its possible alteration through non-invasive treatments

Atopic dermatitis (AD) is a common chronic skin disease that is characterized by intense pruritus and has high impairment of quality of life. AD is often described as "the itch that rashes, rather than the rash that itches". Several studies suggest that mechanisms of central modulation play an important role in the development and maintenance of chronic itch. Therefore, treating the neurosensory aspects of itch is an important part in the management of chronic itch. However, little attention has been paid to the role of the central nervous system in the processing of itch in AD. Targeting itch-related anatomical structures in the brain with non-invasive treatments such as psychological interventions and transcranial Direct Current Stimulation (tDCS) could have an antipruritic effect in AD. Therefore, in this review article, we discuss the current progress in brain imaging research of itch, as well as the efficacy of non-invasive interventions for itch relief in this patient group.

Caffeic acid exhibits anti-pruritic effects by inhibition of multiple itch transmission pathways in mice

Itch is an unpleasant sensation that evokes a desire to scratch. Although often regarded as a trivial 'alarming' sensation, itch may be debilitating and exhausting, leading to reduction in quality of life. In the current study, the question of whether caffeic acid can be used to alleviate itch sensation induced by various pruritic agents, including histamine, chloroquine, SLIGRL-NH2, and β-alanine was investigated. It turned out that histamine-induced intracellular calcium increase was significantly blocked by caffeic acid in HEK293T cells that express H1R and TRPV1, molecules required for transmission of histamine-induced itch in sensory neurons. In addition, inhibition of histamine-induced intracellular calcium increase by caffeic acid was demonstrated in primary cultures of mouse dorsal root ganglion (DRG). When chloroquine, an anti-malaria agent known to induce histamine-independent itch - was used, it was also found that caffeic acid inhibits the induced response in both DRG and HEK293T cells that express MRGPRA3 and TRPA1, underlying molecular entities responsible for chloroquine-mediated itch. Likewise, intracellular calcium changes by SLIGRL-NH2 - an itch-inducing agent via PAR2 and MRGPRC11 - were decreased by caffeic acid as well. However, it was found that caffeic acid is not capable of inhibiting β-alanine-induced responses via its specific receptor MRGPRD. Finally, in vivo scratching behavior tests showed that caffeic acid indeed has anti-scratching effects against histamine, chloroquine, and SLIGRL-NH2 administration but not by β-alanine. Overall, the current study demonstrated that caffeic acid has anti-itch effects by inhibition of multiple itch mechanisms induced by histamine, chloroquine and SLIGRL-NH2.

Chloroquine-induced scratching is mediated by NO/cGMP pathway in mice

Chloroquine (CQ), a 4-aminoquinoline drug, has long been used in the treatment and prevention of malaria. However its side effect generalized pruritus contributes to treatment failures, and consequently results in the development of chloroquine resistant strains of Plasmodium falciparum. It was proposed that the administration of CQ correlated with increase in nitric oxide (NO) production. Nitric oxide is involved in some pruritic disorders such as atopic dermatitis, psoriasis and scratching behavior evoked by pruritogens like substance P. Therefore, the aim of this study was to investigate the involvement of NO/cGMP pathway in CQ-induced scratching in mice. Scratching behaviors were recorded by a camera after intradermal (ID) injection of CQ in the shaved rostral back of the mice. The results obtained show that CQ elicited scratching in a dose-dependent manner with a peak effective dose of 400μg/site. Injection of non-specific NOS inhibitor, N-nitro-l-arginine methyl ester or neuronal NOS selective inhibitor and 7-nitroindazole, reduced CQ-induced scratching significantly. On the other hand, administration of aminoguanidine as inducible NOS inhibitor has no inhibitory effect on this behavior. Also, injection of l-arginine as a precursor of NO significantly increased this response. Conversely, accumulation of cGMP by sildenafil as a selective phosphodiesterase type 5 inhibitor, potentiated the scratching behavior by CQ. This study therefore shows that CQ-induced scratching behavior is mediated by the NO/cGMP pathway.

Zyklophin, a short-acting kappa opioid antagonist, induces scratching in mice

It has been shown previously that norbinaltorphimine (norBNI) and 5'-guanidinonaltrindole (5'-GNTI), long-acting kappa opioid receptor (KOPR) antagonists, cause frenzied scratching in mice [1,2]. In the current study, we examined if zyklophin, a short-acting cyclic peptide KOPR antagonist, also elicited scratching behavior. When injected s.c. in the nape of the neck of male Swiss-Webster mice, zyklophin at doses of 0.1, 0.3 and 1mg/kg induced dose-related hindleg scratching of the neck between 3 and 15 min after injection. Pretreating mice with norBNI (20mg/kg, i.p.) at 18-20 h before challenge with zyklophin (0.3mg/kg) did not markedly affect scratching. Additionally, KOPR-/- mice given 0.3mg/kg of zyklophin displayed similar levels of scratching as wild-type animals. The absence of KOPR in KOPR-/- mice was confirmed with ex vivo radioligand binding using [(3)H]U69,593. Taken together, our data suggest that the presence of kappa receptors is not required for the excessive scratching caused by zyklophin. Thus, zyklophin, similar to the structurally different KOPR antagonist 5'-GNTI, appears to act at other targets to elicit scratching and potentially the sensation of itch.

Controlled nanodot fabrication by rippling polycarbonate surface using an AFM diamond tip

The single scratching test of polymer polycarbonate (PC) sample surface using an atomic force microscope (AFM) diamond tip for fabricating ripple patterns has been studied with the focus on the evaluation of the effect of the tip scratching angle on the pattern formation. The experimental results indicated that the different oriented ripples can be easily machined by controlling the scratching angles of the AFM. And, the effects of the normal load and the feed on the ripples formation and their periods were also studied. Based on the ripple pattern formation, we firstly proposed a two-step scratching method to fabricate controllable and oriented complex three-dimensional (3D) nanodot arrays. These typical ripple formations can be described via a stick-slip and crack formation process.

Roles of glutamate, substance P, and gastrin-releasing peptide as spinal neurotransmitters of histaminergic and nonhistaminergic itch

We investigated roles for substance P (SP), gastrin-releasing peptide (GRP), and glutamate in the spinal neurotransmission of histamine-dependent and -independent itch. In anesthetized mice, responses of single superficial dorsal horn neurons to intradermal (i.d.) injection of chloroquine were partially reduced by spinal application of the α-amino-3-hydroxy-5-methyl-4-isoxazole proprionate acid (AMPA)/kainate antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Co-application of CNQX plus a neurokinin-1 (NK-1) antagonist produced stronger inhibition, while co-application of CNQX, NK-1, and GRP receptor (GRPR) antagonists completely inhibited firing. Nociceptive-specific and wide dynamic range-type neurons exhibited differential suppression by CNQX plus either the GRPR or NK-1 antagonist, respectively. Neuronal responses elicited by i.d. histamine were abolished by CNQX alone. In behavioral studies, individual intrathecal administration of a GRPR, NK-1, or AMPA antagonist each significantly attenuated chloroquine-evoked scratching behavior. Co-administration of the NK-1 and AMPA antagonists was more effective, and administration of all 3 antagonists abolished scratching. Intrathecal CNQX alone prevented histamine-evoked scratching behavior. We additionally employed a double-label strategy to investigate molecular markers of pruritogen-sensitive dorsal root ganglion (DRG) cells. DRG cells responsive to histamine and/or chloroquine, identified by calcium imaging, were then processed for co-expression of SP, GRP, or vesicular glutamate transporter type 2 (VGLUT2) immunofluorescence. Subpopulations of chloroquine- and/or histamine-sensitive DRG cells were immunopositive for SP and/or GRP, with >80% immunopositive for VGLUT2. These results indicate that SP, GRP, and glutamate each partially contribute to histamine-independent itch. Histamine-evoked itch is mediated primarily by glutamate, with GRP playing a lesser role. Co-application of NK-1, GRP, and AMPA receptor antagonists may prove beneficial in treating chronic itch.

Nobiletin and tangeretin ameliorate scratching behavior in mice by inhibiting the action of histamine and the activation of NF-κB, AP-1 and p38

Nobiletin and tangeretin are polymethoxy flavonoids that are abundantly present in the pericarp of Citrus unshiu (family Rutaceae) and the fruit of Citrus depressa (family Rutaceae). They exhibit various biological activities, including anti-inflammatory and anti-asthmatic effects. To evaluate the anti-allergic effects of nobiletin and tangeretin, we measured their inhibitory effects in histamine- or compound 48/80-induced scratching behavioral mice. Nobiletin and tangeretin potently inhibited scratching behavior, as well as histamine-induced vascular permeability. Furthermore, they inhibited the expression of the allergic cytokines, IL-4 and TNF-α as well as the activation of their transcription factors NF-κB, AP-1 and p38 in histamine-stimulated skin tissues. They also inhibited the expression of IL-4 and TNF-α and the activation of NF-κB and c-jun in PMA-stimulated RBL-2H3 cells. Furthermore, nobiletin and tangeretin inhibited protein kinase C (PKC) activity and the IgE-induced degranulation of RBL-2H3 cells. These agents showed potent anti-histamine effect through the Magnus test when guinea pig ileum was used. Based on these results, nobiletin and tangeretin may ameliorate scratching behavioral reactions by inhibiting the action of histamine as well as the activation of the transcription factors NF-κB and AP-1 via PKC.