Intradermal Injection Of Histamine Research Articles

Chitosan-coated alginate (CCA) nanoparticles for augmentation of topical antihistaminic activity of diphenhydramine: in-vitro optimization, skin histopathology and pharmacodynamic studies with in vitro/in vivo correlation

Objective The aim of the present study was to formulate chitosan-coated alginate nanoparticles containing the drug diphenhydramine hydrochloride (DHH). Significance Diphenhydramine hydrochloride (DHH) is the prototype of H1-antihistaminic drugs. It is a lipophilic drug, that easily crosses the blood–brain barrier when taken orally causing decrements in alertness and performance. Multiple applications of topical drug products are required. Thus, drug incorporation in nanocarriers would increase the skin penetration powers increasing the drug efficacy. Methods Chitosan-coated alginate (CCA) nanoparticles were prepared via polyelectrolyte complex technique adopting 23 full factorial designs. Three factors, namely, alginate concentration, drug-to-alginate ratio and CaCl2 volume, each in two levels were studied. The prepared formulae were evaluated utilizing entrapment efficiency (EE), particle size (PS), polydispersity index (PDI), zeta potential (ZP) and in vitro release. The characterization process was then followed by optimization. Results At alginate conc. of 1%, drug to alginate ratio of 2:1 and CaCl2 volume of 4 mL, NP8 was chosen as a candidate formula. Histopathological examination on shaved rat dorsal skin disclosed the safety of NP8 with no signs of necrosis or even inflammation. The enhanced topical delivery of diphenhydramine hydrochloride enclosed in the developed nanoparticles was further proved by induction of allergic reaction using intradermal histamine injection. The results revealed the superior ability of NP8 to decrease the diameter of the formed wheal in comparison to the marketed DHH product. Conclusion Thus, CCA nanoparticles are considered candidate nanocarriers for fortifying the topical antihistaminic activity of DHH.

MrgprA3-expressing pruriceptors drive pruritogen-induced alloknesis through mechanosensitive Piezo2 channel

Although touch and itch are coded by distinct neuronal populations, light touch also provokes itch in the presence of exogenous pruritogens, resulting in a phenomenon called alloknesis. However, the cellular and molecular mechanisms underlying the initiation of pruritogen-induced mechanical itch sensitization are poorly understood. Here, we show that intradermal injections of histamine or chloroquine (CQ) provoke alloknesis through activation of TRPV1- and MrgprA3-expressing prurioceptors, and functional ablation of these neurons reverses pruritogen-induced alloknesis. Moreover, genetic ablation of mechanosensitive Piezo2 channel function from MrgprA3-expressing prurioceptors also dampens pruritogen-induced alloknesis. Mechanistically, histamine and CQ sensitize Piezo2 channel function, at least in part, through activation of the phospholipase C (PLC) and protein kinase C-δ (PKCδ) signaling. Collectively, our data find a TRPV1+/MrgprA3+ prurioceptor-Piezo2 signaling axis in the initiation of pruritogen-induced mechanical itch sensitization in the skin.

Effect of glycerin on immediate cutaneous reactions of histamine (positive) and phosphate-buffered saline (negative) controls in intradermal skin testing of healthy dogs: A randomised, blinded study.

Glycerinated allergen extracts contain 50% glycerin, an excellent preservative. While glycerin is a recognised irritant in humans, the utility of glycerinated extracts for intradermal testing has not been validated in dogs. To determine and compare the effects of glycerin on immediate cutaneous reactions to intradermal injections of histamine and saline in healthy dogs. Eight healthy laboratory beagles. The study was designed as a randomised, blinded study. Intradermal injections of histamine (positive control) and saline (negative control) in aqueous and glycerinated (50%) forms were performed on the right thorax. Global wheal scores (GWS) at 20 min were evaluated by two independent investigators blinded to the interventions. There were no wheal and flare reactions observed after the intradermal injections of phenolated saline. By contrast, 50% glycerosaline injections induced erythema and induration in all dogs. Global wheal scores were significantly higher in aqueous histamine (Friedman test, p< 0.0001) and 50% glycerinated histamine (Friedman test, p= 0.0084) compared to phenolated saline controls. Interestingly, only aqueous histamine (Friedman test, p= 0.01) had significantly higher GWS than 50% glycerosaline injections, while no significant difference in GWS between 50% glycerinated histamine and 50% glycerosaline groups was observed (Friedman test, p= 0.59). This study demonstrates that intradermal injection of 50% glycerosaline induces erythema and induration skin reactions in healthy dogs that can mimic positive reactions to allergenic extracts. Further dilutions of glycerinated positive and negative control solutions need to be optimised for intradermal testing in dogs.

Lack of Clinical Relevance of Bilastine-Food Interaction in Healthy Volunteers: A Wheal and Flare Study

Introduction: The aim of this study was to compare the pharmacodynamic activity of bilastine administered under fasting and fed conditions in healthy volunteers. Methods: In this randomized, open-label, two-period, crossover study involving 24 healthy subjects, once-daily oral bilastine 20 mg was administered for 4 days under fasting and fed conditions, with a 7-day washout period. Bilastine plasma concentrations were measured for 24 h after the first and fourth doses in each period. Pharmacodynamic activity was assessed by wheal and flare surface inhibition and subjective assessment of itching, after intradermal injection of histamine 5 μg. Results: When administered under fed versus fasting conditions, exposure to bilastine 20 mg decreased (mean maximum plasma concentration and area under the curve from time 0 to 24 h decreased by 34.27% and 32.72% [day 1], respectively, and 33.08% and 28.87% [day 4]). Despite this, the antihistaminic effect of bilastine 20 mg was not altered by food. On day 1, as assessed by wheal and flare surface inhibition, the maximum effect and duration of action of bilastine did not differ to a significant extent between fasting and fed conditions, with only a short 30-min delay in the onset of wheal inhibition. At steady state (day 4), bilastine’s pharmacodynamic effects were not significantly affected under fasting or fed conditions. Conclusion: The pharmacokinetic interaction of bilastine with food does not imply a significant reduction of its peripheral antihistaminic efficacy. Despite a slight delay in onset of action on the first treatment day, the global clinical efficacy of bilastine is not affected by coadministration with food.

Effect of diphenhydramine and cetirizine on immediate and late-phase cutaneous allergic reactions in healthy dogs: a randomized, double-blinded crossover study.

Currently, there is insufficient evidence to confirm oral diphenhydramine (DPH) efficacy to prevent mast cell degranulation and histamine release in dogs. To determine and compare the effects oral of DPH and cetirizine on the immediate- and late-phase cutaneous allergic reactions in healthy dogs. Twelve healthy laboratory beagle dogs. The study was designed as a randomized, double-blinded crossover study in which each dog served as its own control; twice-daily oral DPH (2.2mg/kg) or cetirizine (2mg/kg) were given for six days with a two week washout period. Intradermal injections of histamine, compound 48/80 (positive control) and saline (negative control) were performed on the right thorax 10days before drug administration (baseline), during oral antihistamine administration on Day 6 and 10days after last medication dosage. Global wheal scores (GWS) at 20min and late-phase reactions (LPR) at 6h post-injection were evaluated by an investigator blinded to the drug and the interventions. Treatment with cetirizine significantly reduced histamine and compound 48/80 GWS and LPR compared to baseline; there was no significant difference for DPH. In all dogs, oral DPH and cetirizine reached plasma concentrations considered therapeutic in people. No adverse effect or behavioural changes were observed during the study. In conclusion, oral cetirizine was effective in preventing cutaneous allergic reactions without any obvious adverse effects in dogs. Oral DPH failed to show an inhibitory effect despite attaining plasma drug concentrations that are considered effective in people.

Bulleyaconitine A Inhibits Itch and Itch Sensitization Induced by Histamine and Chloroquine

Itch (pruritus), specifically chronic itch associated with disease conditions, significantly impairs the patient’s quality of life. At present, the mechanisms underlying this aversive experience are still unclear, and the effective treatment of itch is largely unmet. Here, we report that intragastrical administration of bulleyaconitine A (BLA), which has been used for treating chronic pain for 30 years in China, inhibited itch-like behaviors induced by intradermal injection of histamine and chloroquine in mice and rats, dose-dependently. We found that a single application of the pruritic agents at the skin region innervated by the sural nerve induced long-term potentiation (LTP) of C-fiber field potentials evoked by the stimulation of the same nerve in the spinal dorsal horn of rats. The spinal LTP was remarkably reversed by the spinal application of either BLA or gastrin-releasing peptide receptor (GRPR) antagonist (PD176252). The effect of PD176252 was completely occluded by BLA, while the effect of BLA was only partially occluded by PD176252. Repetitive injection (daily, for four days) of either histamine or chloroquine in the back of the neck enhanced scratching behaviors progressively, and the itch sensitization persisted for at least one week after the discontinuation of the injections. The behavioral change was accompanied with the potentiation of C-fiber synaptic transmission in the dorsal horn. Both the itch sensitization and synaptic potentiation were substantially attenuated by intragastrical BLA. Together, BLA was effective in inhibiting histamine-dependent and histamine-independent itches, and the mechanisms underlying these effects were involved but not limited to the inhibition of gastrin-releasing peptide (GRP)–GRPR signaling in the spinal dorsal horn.

Opposing effects of cervical spinal cold block on spinal itch and pain transmission.

Inactivation of descending pathways enhanced responses of spinal dorsal horn neurons to noxious stimuli, but little is known regarding tonic descending modulation of spinal itch transmission. To study effects of cervical spinal cold block on responses of dorsal horn neurons to itch-evoking and pain-evoking stimuli, single-unit recordings were made from superficial dorsal horn wide dynamic range and nociceptive-specific-type neurons in pentobarbital-anesthetized mice. Intradermal histamine excited 17 units. Cold block starting 1 minute after intradermal injection of histamine caused a marked decrease in firing. The histamine-evoked response during and following cold block was significantly lower compared with control histamine-evoked responses in the absence of cold block. A similar but weaker depressant effect of cold block was observed for dorsal horn unit responses to chloroquine. Twenty-six units responded to mustard oil allyl isothiocyanate (AITC), with a further significant increase in firing during the 1-minute period of cold block beginning 1 minute after AITC application. Activity during cold block was significantly greater compared with the same time period of control responses to AITC in the absence of cold block. Ten units’ responses to noxious heat were significantly enhanced during cold block, while 6 units’ responses were reduced and 18 unaffected. Cold block had no effect on mechanically evoked responses. These results indicate that spinal chemonociceptive transmission is under tonic descending inhibitory modulation, while spinal pruriceptive transmission is under an opposing, tonic descending facilitatory modulation.

The anti-inflammatory effect of topical tofacitinib on immediate and late-phase cutaneous allergic reactions in dogs: a placebo-controlled pilot study.

Topical Janus kinase (JAK) inhibition is a promising therapeutic target for several inflammatory skin diseases of humans. To evaluate the anti-inflammatory effect of tofacitinib, a JAK 1/3 inhibitor, on immediate and late-phase skin reactions in dogs. Five healthy laboratory beagle dogs. Topical tofacitinib (total daily dosage: 0.5 mg/cm2 ) or its gel vehicle were applied on either the left or right lateral thorax of each dog for eight days. Three days before application and after eight days of topical treatment, intradermal injections of histamine and anticanine-IgE antibodies were performed on both sides; they were evaluated by an investigator blinded to the interventions. The tofacitinib gel was well-tolerated; one dog developed mild erythema at Day 5 that resolved by the next application. Treatment with tofacitinib reduced histamine and anticanine-IgE global wheal scores (one-way ANOVA, P ≤ 0.005 for both) compared to baseline; there was no significant difference for the vehicle placebo (histamine; P = 0.163; IgE, P = 0.223). Late-phase reactions (LPRs) were markedly, but not significantly reduced after tofacitinib treatment (P = 0.071). A blinded histological evaluation of 6 h-anti-IgE-associated LPRs revealed a significant reduction in the total leucocyte superficial dermal cellularity (P = 0.022), as well as eosinophil (P = 0.022) and mast cell (P = 0.022) counts at tofacitinib-treated sides compared with pretreatment values. Post-treatment complete blood counts and serum chemistry profiles did not show relevant tofacitinib-induced changes. Our observations suggest that topical tofacitinib exerts an inhibitory effect on activated canine skin-emigrating immune cells; this drug should be investigated further as a topical immunosuppressive drug in dogs.

Influence of glucocorticoids on a time-of-day-dependent variation in intradermal reactivity to histamine in dogs

The objectives of this study were to determine daily variation in intradermal reactivity to histamine in dogs and to evaluate a potential influence of glucocorticoids on reactivity. Wheal sizes formed after intradermal injections of histamine were measured every 6 h during a single 24 h period in six healthy dogs. To determine whether glucocorticoids were implicated in daily variation, intradermal reactivity to histamine was evaluated at 9:00 h and at 21:00 h during a single day in dogs that received oral prednisolone (a synthetic glucocorticoid) or oral trilostane (an inhibitor of endogenous glucocorticoid synthesis). Finally, the time required for the histamine reaction to diminish after an intravenous injection of hydrocortisone was also assessed.A significant time-of-day-dependent variation in intradermal reactivity to histamine was detected in dogs, with a larger wheal size observed at 9:00 h than at 21:00 h. Administration of prednisolone or trilostane disrupted this variation. Intradermal reactivity to histamine was significantly reduced 6 h after an intravenous injection of hydrocortisone. These results suggest that glucocorticoid secretion from the adrenal glands could be involved in the regulation of daily variation in histamine-mediated reactions in dogs.

Identification of a Neuronal Receptor Controlling Anaphylaxis.

Allergic reactions can in severe cases induce a state of circulatory shock referred to as anaphylaxis. Histamine, the primary mediator of this condition, is released from immune cells, and, therefore, anaphylaxis has so far been considered an immune system disorder. However, we here show that the glutamatergic receptor mGluR7, expressed on a subpopulation of both peripheral and spinal cord neurons, controls histamine-induced communication through calcium-dependent autoinhibition with implications for anaphylaxis. Genetic ablation of mGluR7, and thus altered regulation of histamine-sensing neurons, caused an anaphylaxis-like state in mGluR7(-/-) mice, which could be reversed by antagonizing signaling between neurons and mast cells but not by antagonizing a central itch pathway. Our findings demonstrate the vital role of nervous system control by mGluR7 in anaphylaxis and open up possibilities for preventive strategies for this life-threatening condition.

Psychophysical Measurements of Itch and Nociceptive Sensations in an Experimental Model of Allergic Contact Dermatitis

Allergic contact dermatitis (ACD) is a common condition that can significantly affect the quality of life. Contact with allergens results in delayed hypersensitivity reactions involving T lymphocytes, with associated skin inflammation and spontaneous itch and nociceptive sensations. However, psychophysical studies of these sensations are lacking. In the present study, we sensitized 8 healthy volunteers to squaric acid dibutyl ester (SADBE). Two weeks later, 1 volar forearm was challenged with SADBE, and the other with acetone vehicle control. Subsequently, participants rated the maximal perceived intensity of spontaneous itch, pricking/stinging, and burning every 6 to 12 hours for 1 week, using the generalized Labeled Magnitude Scale. In the laboratory, they judged stimulus-evoked sensations within and outside the chemically treated area. The SADBE- but not the acetone-treated skin resulted in 1) localized inflammation, with spontaneous itch and nociceptive sensations peaking at 24 to 48 hours after challenge, 2) alloknesis, hyperknesis, and hyperalgesia to mechanical stimuli that were reduced or eliminated by anesthetic cooling of the SADBE-treated area and restored on rewarming, suggesting that sensations and dysesthesias are dependent on ongoing peripheral neural activity, and 3) enhanced itch to intradermal injection of histamine, BAM8-22, or β-alanine. This experimental model of T-cell-mediated inflammation may prove useful in evaluating potential treatments of itch from ACD. PerspectiveIn a model of allergic contact dermatitis, experimentally applied in humans, psychophysical measurements were obtained of persistent, spontaneous itch and enhanced stimulus-evoked itch and pain sensations. These sensory measurements will be useful in the identification of the neural mechanisms underlying inflammatory itch and pain.

Nalfurafine Suppresses Pruritogen- and Touch-evoked Scratching Behavior in Models of Acute and Chronic Itch in Mice

The kappa-opioid agonist, nalfurafine, has been approved in Japan for treatment of itch in patients with chronic kidney disease. We presently investigated if systemic administration of nalfurafine inhibited ongoing or touch-evoked scratching behavior (alloknesis) following acute intradermal injection of histamine or the non-histaminergic itch mediator, chloroquine, in mice. We also investigated if nalfurafine suppressed spontaneous or touch-evoked scratching in an experimental model of chronic dry skin itch. Nalfurafine reduced scratching evoked by histamine and chloroquine. Following acute histamine, but not chloroquine, low-threshold mechanical stimuli reliably elicited directed hindlimb scratching behavior, which was significantly attenuated by nalfurafine. In mice with experimental dry skin, nalfurafine abolished spontaneous scratching but had no effect on alloknesis. Nalfurafine thus appears to be a promising treatment for acute itch as well as ongoing itch of dry skin.

Global Nav1.7 knockout mice recapitulate the phenotype of human congenital indifference to pain.

Clinical genetic studies have shown that loss of Nav1.7 function leads to the complete loss of acute pain perception. The global deletion is reported lethal in mice, however, and studies of mice with promoter-specific deletions of Nav1.7 have suggested that the role of Nav1.7 in pain transduction depends on the precise form of pain. We developed genetic and animal husbandry strategies that overcame the neonatal-lethal phenotype and enabled construction of a global Nav1.7 knockout mouse. Knockouts were anatomically normal, reached adulthood, and had phenotype wholly analogous to human congenital indifference to pain (CIP): compared to littermates, knockouts showed no defects in mechanical sensitivity or overall movement yet were completely insensitive to painful tactile, thermal, and chemical stimuli and were anosmic. Knockouts also showed no painful behaviors resulting from peripheral injection of nonselective sodium channel activators, did not develop complete Freund’s adjuvant-induced thermal hyperalgesia, and were insensitive to intra-dermal histamine injection. Tetrodotoxin-sensitive sodium current recorded from cell bodies of isolated sensory neurons and the mechanically-evoked spiking of C-fibers in a skin-nerve preparation each were reduced but not eliminated in tissue from knockouts compared to littermates. Results support a role for Nav1.7 that is conserved between rodents and humans and suggest several possibly translatable biomarkers for the study of Nav1.7-targeted therapeutics. Results further suggest that Nav1.7 may retain its key role in persistent as well as acute forms of pain.

Extracellular signal-regulated kinase (ERK) activation is required for itch sensation in the spinal cord

BackgroundItch, chronic itch in particular, can have a significant negative impact on an individual’s quality of life. However, the molecular mechanisms underlying itch processing in the central nervous system remain largely unknown.ResultsWe report here that activation of ERK signaling in the spinal cord is required for itch sensation. ERK activation, as revealed by anti-phosphorylated ERK1/2 immunostaining, is observed in the spinal dorsal horn of mice treated with intradermal injections of histamine and compound 48/80 but not chloroquine or SLIGRL-NH2, indicating that ERK activation only occurs in histamine-dependent acute itch. In addition, ERK activation is also observed in 2, 4-dinitrofluorobenzene (DNFB)-induced itch. Consistently, intrathecal administration of the ERK phosphorylation inhibitor U0126 dramatically reduces the scratching behaviors induced by histamine and DNFB, but not by chloroquine. Furthermore, administration of the histamine receptor H1 antagonist chlorpheniramine decreases the scratching behaviors and ERK activation induced by histamine, but has no effect on DNFB-induced itch responses. Finally, the patch-clamp recording shows that in histamine-, chloroquine- and DNFB-treated mice the spontaneous excitatory postsynaptic current (sEPSC) of dorsal horn neurons is increased, and the decrease of action potential threshold is largely prevented by bathing of U0126 in histamine- and DNFB-treated mice but not those treated with chloroquine.ConclusionOur results demonstrate a critical role for ERK activation in itch sensation at the spinal level.

Sex-related differences in SLIGRL-induced pruritus in mice

AimsPruritus is a common symptom of skin diseases, and is associated with impaired sleep quality and a considerable reduction in the patient's quality of life. Recently, it was reported that there are sex-specific differences in scratching behavior in chronic pruritus patients. Namely, female chronic pruritus patients scratch more and have significantly more scratch lesions than male patients. However, few animal studies have examined sex-related differences in scratching behavior. Thus, the present work investigated sex-related differences in animal pruritus using pruritogens, which are often used to create experimental animal models of itching. Main methodsAcute pruritus was induced in ICR mice by a single intradermal injection of histamine, 4-methylhistamine, serotonin, compound 48/80, substance P (SP), or the proteinase-activated receptor-2 (PAR-2)-activating peptide SLIGRL-NH2. Chronic pruritus was induced by 5weeks of the repeated application of 2,4,6-trinitro-1-chlorobenzene (TNCB) to BALB/c mice. Key findingsFemale mice showed significantly higher scratching counts in SLIGRL-NH2-induced pruritus than male mice. Conversely, there was no obvious sex-related difference in scratching behavior for the other pruritogens examined. SignificanceThese results indicate that sex-related differences may exist in the pruritogen-responsive neurons that transmit the itch signal induced by SLIGRL-NH2, but not by histamine or 5-HT.

The Receptor LMIR3 Negatively Regulates Mast Cell Activation and Allergic Responses by Binding to Extracellular Ceramide

Mast cells (MCs) are key effector cells in allergic reactions. However, the inhibitory mechanism that prevents excessive activation of MCs remains elusive. Here we show that leukocyte mono-immunoglobulin-like receptor 3 (LMIR3; also called CD300f) is a negative regulator of MC activation in vivo. LMIR3 deficiency exacerbated MC-dependent allergic responses in mice, including anaphylaxis, airway inflammation, and dermatitis. Both physical binding and functional reporter assays via an extracellular domain of LMIR3 showed that several extracellular lipids (including ceramide) and lipoproteins were possible ligands for LMIR3. Importantly, MCs were frequently surrounded by extracellular ceramide in vivo. Upon engagement of high-affinity immunoglobulin E receptor, extracellular ceramide-LMIR3 binding inhibited MC activation via immunoreceptor tyrosine-based inhibitory and switch motifs of LMIR3. Moreover, pretreatment with LMIR3-Fc fusion protein or antibody against either ceramide or LMIR3 interfered with this binding in vivo, thereby exacerbating passive cutaneous anaphylaxis. Thus, the interaction between extracellular ceramide and LMIR3 suppressed MC-dependent allergic responses.

Antihistamines do not inhibit the wheal induced by the intradermal injection of autologous serum in resistant chronic idiopathic urticaria

Some patients with chronic idiopathic urticaria (CIU) are resistant to conventional doses of antihistamines (AHs). This study was designed to check whether the skin wheal and flare reaction produced by the intradermal injection of autologous serum (AS) and by histamine differs in AH-resistant and AH responder CIU patients. CIU patients with treatment failure under fexofenadine at 180 mg q.d. increased their daily dose of AH to 4 tablets daily. Those with significant improvement of urticaria activity score under fexofenadine at 180 mg were included in the CIU group. Subjects with treatment failure despite a full 8-week fourfold fexofenadine treatment were included in the resistant CIU (R-CIU group). The control group consisted of sex- and age-matched patents with allergic rhinitis. The AS skin test and intradermal histamine-induced wheal and flare reaction were performed at baseline (without AH), after 8 and 16 weeks (under AH treatment). Forty-six subjects were included in the CIU group, 21 were in the R-CIU group, and 44 were in the control group. Under AH therapy, the skin reaction to intradermal histamine injection was significantly diminished in all study groups. In the R-CIU group, fexofenadine at 180 mg did not suppress AS-induced wheal reaction (5.96 ± 2.25 mm; p = 0.85), and with a fourfold AH dose some reduction of AS-induced wheal (3.79 ± 1.74 mm; p = 0.008) was observed but remained larger than in the CIU (2.31 ± 1.12; p = 0.006) and control groups (2.52 ± 1.36; p = 0.037). AHs do not inhibit the wheal induced by the intradermal injection of AS in R-CIU.

Congenital insensitivity to pain and anhidrosis: A case report from South India

Congenital insensitivity to pain with anhidrosis, also known as hereditary sensory and autonomic neuropathy type IV, is an autosomal recessive disorder characterized by the congenital lack of pain sensation, inability to sweat, episodes of recurrent hyperpyrexia, mental retardation, and self-mutilating behavior. It is an extremely rare disorder with only a handful of reports from India. A five- year- old boy, born to second-degree consanguineous parents after uneventful antenatal period, presented to us with history of recurrent unexplained fever, recurrent ulcers in the lower limbs, insensitivity to painful stimuli (like injections, vaccination) and self-mutilating behavior from early childhood. Cutaneous examination showed multiple ulcers, loss of teeth, loss of tip of the tongue (due to biting), scarring of finger tips, xerosis and lichenification. Sensory examination showed complete loss of pain and temperature sensations, but fine touch and vibration were preserved. Deep tendon reflexes were normal. Evaluation for Hansen's disease was non-contributory. An intradermal injection of histamine did not show any flare response. Based on clinical as well as compatible histological features a diagnosis of congenital insensitivity to pain with anhidrosis was made. The ulcers were treated with appropriate antibiotics and daily dressings. The parents were counseled about appropriate care of the child.

Glycyrrhetinic acid prevents cutaneous scratching behavior in mice elicited by substance P or PAR-2 agonist

Although glycyrrhetinic acid (GA) has been used for the prevention of itch in chronic dermatitis, the mechanism underlying the antipruritic effects of GA is still unclear. Recently, several mediators other than histamine, such as substance P and tryptase, were found to participate in chronic itch. Here, we investigated the effect of GA on pruritus induced by various pruritic agents including histamine in mice. We also determined the level of leukotriene (LT)B(4) in mouse skin injected with substance P in an effort to uncover part of the antipruritic mechanism of GA. Scratching events were counted for 10 min after intradermal injection of histamine, substance P (100 nmol per site each), protease-activated receptor-2 (PAR-2) agonistic peptide (50 nmol per site), or LTB(4) (0.03 nmol per site) with or without GA (4 nmol per site) into male ICR mice. Levels of LTB(4) in the skin after injection of substance P were determined by ELISA. GA did not suppress scratching behavior induced by histamine and LTB(4), but markedly and dose-dependently suppressed that induced by substance P and PAR-2 agonistic peptide. LTB(4) levels in skin elevated by substance P were lowered by GA. These data support the efficacy of GA in counteracting itch in chronic dermatitis because GA reduced scratching behavior induced by substance P and PAR-2 agonistic peptide. GA may exert antipruritic effects via inhibition of LTB(4) production in skin.

EFFECT OF ADRENALECTOMY ON THE RESPONSE OF RAT SKIN TO AN INTRADERMAL INJECTION OF HISTAMINE AND 5-HYDROXYTRYPTAMINE.

EFFECT OF ADRENALECTOMY ON THE RESPONSE OF RAT SKIN TO AN INTRADERMAL INJECTION OF HISTAMINE AND 5-HYDROXYTRYPTAMINE.