Optimization of a method for determination of phenolic acids in exotic fruits by capillary electrophoresis

In this work, the separation of nine phenolic acids (benzoic, caffeic, chlorogenic, p-coumaric, ferulic, gallic, protocatechuic, syringic, and vanillic acid) was approached by a 3² factorial design in electrolytes consisting of sodium tetraborate buffer (STB) in the concentration range of 10–50 mmol L⁻¹ and methanol in the volume percentage of 5–20%. Derringer's desirability functions combined globally were tested as response functions. An optimal electrolyte composed by 50 mmol L⁻¹ tetraborate buffer at pH 9.2, and 7.5% (v/v) methanol allowed baseline resolution of all phenolic acids under investigation in less than 15 min. In order to promote sample clean up, to preconcentrate the phenolic fraction and to release esterified phenolic acids from the fruit matrix, elaborate liquid–liquid extraction procedures followed by alkaline hydrolysis were performed. The proposed methodology was fully validated (linearity from 10.0 to 100 μg mL⁻¹, R² > 0.999; LOD and LOQ from 1.32 to 3.80 μg mL⁻¹ and from 4.01 to 11.5 μg mL⁻¹, respectively; intra-day precision better than 2.8% CV for migration time and 5.4% CV for peak area; inter-day precision better than 4.8% CV for migration time and 4.8–11% CV for peak area; recoveries from 81% to 115%) and applied successfully to the evaluation of phenolic contents of abiu-roxo (Chrysophyllum caimito), wild mulberry growing in Brazil (Morus nigra L.) and tree tomato (Cyphomandra betacea). Values in the range of 1.50–47.3 μg g⁻¹ were found, with smaller amounts occurring as free phenolic acids.     

Development of ultra fast liquid chromatographic method for simultaneous determination of nitrendipine and carvone in skin diffusate samples

A simple and sensitive reverse phase ultra fast liquid chromatographic (UFLC) method for simultaneous determination of nitrendipine and carvone in skin diffusate samples and microemulsions was developed and validated. The separation was achieved using a gradient mobile phase, on an Onyx column. The eluents were monitored by photodiode array detection. The linearity ranges of proposed method were 0.125–50 μg mL⁻¹ and 0.125–30 μg mL⁻¹ for nitrendipine and carvone respectively. The intra-day and inter-day coefficient of variation and percent error values of the assay method were less than 10%. The method was found to be precise, accurate, and specific during the study. The method was successfully applied for simultaneous estimation of nitrendipine and carvone in ex vivo skin diffusate samples and microemulsions.     

Development and validation of a reverse phase liquid chromatography method for the quantification of rasagiline mesylate in biodegradable PLGA microspheres

In the present study, a reverse phase high performance liquid chromatographic method was developed and validated for the determination of rasagiline mesylate in biodegradable microspheres. Chromatographic separation was carried out on a RP-18 column using a mobile phase consisting of acetonitrile:water (5:95, v/v) adjusted at pH 3.1. Flow rate was 1.0 ml min⁻¹ and UV detection at 290 nm. Acyclovir was used as the internal standard. The calibration curve was linear over the range 0.5–20.0 μg ml⁻¹. R.S.D. for precision was <1.8%. Accuracy ranged between 99.01% and 102.55% with a R.S.D. lower than 1.3%. LOD and LOQ were 0.07 μg ml⁻¹ and 0.23 μg ml⁻¹, respectively. The method was simple, rapid, and easy to apply, making it very suitable for routine analysis of rasagiline mesylate in biodegradable PLGA microspheres. It could be also used with reliability for the determination of the drug in other pharmaceutical dosage forms.     

Biphasic effects of mianserin and desipramine on serotonin-evoked current and Cl efflux in Xenopus oocytes

Serotonin (5-HT, 1 μM) elicited two phases of Cl⁻ inward current in Xenopus oocytes injected with rat brain mRNA: a transient current (T-current), which was generated rapidly (within 1 min), and a sustained current (S-current), which persisted for 10 min. Each type of 5-HT-evoked response was time-dependent after mRNA injection. The T-current was generated at 20-30 h and the S-current at 30–40 h. Although mianserin at 0.1 μ M completely inhibited the T-current, 10 μ M mianserin was required to suppress the S-current. 5-HT also caused Cl⁻ efflux from oocytes preloaded with ³⁶Cl⁻, Cl⁻ efflux during 1 min, corresponding to the T-current, was inhibited by 0.1 μ M mianserin. A higher concentration of mianserin (10 μ M) was required to block the efflux for 10 min, corresponding to the S-current, as well as the current response. Desipramine selectively inhibited the T-current and Cl⁻ efflux for 1 min. The mechanisms underlying the different sensitivity to mianserin of oocytes injected with rat brain mRNA are discussed.     

Antioxidant activities, metal contents, total phenolics and flavonoids of seven Morchella species

Seven Morchella species were analyzed for their antioxidant activities in different test systems namely β-carotene/linoleic acid, DPPH, reducing power, chelating effect and scavenging effect (%) on the stable ABTS⁺, in addition to their heavy metals, total phenolic and flavonoid contents. In β-carotene/linoleic acid system, the most active mushrooms were M. esculenta var. umbrina and M. angusticeps. In the case of DPPH, methanol extract of M. conica showed high antioxidant activity. The reducing power of the methanol extracts of mushrooms increased with concentration. Chelating capacity of the extracts was also increased with the concentration. On the other hand, in 40 μg ml⁻¹ concentration, methanol extract of M. conica, exhibited the highest radical scavenging activity (78.66 ± 2.07%) when reacted with the ABTS⁺ radical. Amounts of seven elements (Cu, Mn, Co, Zn, Fe, Ca, and Mg) and five heavy metals (Ni, Pb, Cd, Cr, and Al) were also determined in all species. M. conica was found to have the highest phenolic content among the samples. Flavonoid content of M. rotunda was also found superior (0.59 ± 0.01 μg QEs/mg extract).     

The effects of dietary nickel exposure on growth and reproduction of Daphnia magna

Although there is growing evidence that dietborne metals can be toxic to various aquatic species, there is still insufficient knowledge to integrate this information in environmental risk assessment procedures. In this study, we investigated the effects of a 21-day exposure of Daphnia magna to a control diet (i.e. the green alga Pseudokirchneriella subcapitata containing <4.0 μg Ni/g dry wt) and five diets with elevated Ni concentrations (i.e. the same alga contaminated with Ni burdens between 33.7 and 837 μg Ni/g dry wt). A significant accumulation of dietborne Ni in D. magna, i.e. between 49.6 and 72.5 μg Ni/g dry wt, was observed when they were fed with diets containing between 85.6 and 837 μg Ni/g dry wt. This was paralleled by a significant reduction of reproduction (by 33.1%), measured as the total number of juvenile offspring per female and growth (by 9.1%), measured as the carapax length of 21-day-old females. Life-history analysis showed that the time to first brood of Ni exposed organisms was between 7.8 and 8.2 days, and occurred 0.7–1.1 days earlier than for the control organisms (time to first brood = 8.9 days). The number of offspring in the first brood was significantly reduced (by 21–33% compared to the control) in all dietary treatments. Longer exposure (≥8.9 days, i.e. from the second brood onwards) led to a reduction of brood size only when given diets containing 85.6 and 837 μg Ni/g dry wt. The results suggest that a variety of mechanisms may be involved in the effects of dietary Ni exposure, including altered resource allocation or targeted reproductive inhibition. While Ni exposure clearly altered the quality of the diet (measured as essential ω3 polyunsaturated fatty acid content and C:P ratio), we found no conclusive evidence that these diet quality shifts could have affected growth or total reproductive output. More research is required to fully understand the mechanisms of Ni toxicity associated with the dietary exposure route.     

Chiral resolution of the enantiomers of new selective CB2 receptor agonists by liquid chromatography on amylose stationary phases

Analytical HPLC methods using derivatized amylose chiral stationary phases, Chiralpak AD-H and Chiralpak AS, were developed for the direct enantioseparation of eight substituted 4-oxo-1,4-dihydroquinoline-3-carboxamide derivatives with one stereogenic center. Baseline separation (R_s > 1.5) was always achieved on amylose based Chiralpak AD-H column to the difference with Chiralpak AS. Using UV detection, a linear response was observed within a 180–420 μmol L⁻¹ concentration range (r² > 0.991) for three racemic compounds 1, 3 and 4 with best pharmacological potentials; repeatability, limit of detection (LD) and quantification (LQ) were also determined: LD varied, for the solutes, from 0.36 to 2.56 μmol L⁻¹. Finally, the enantiopurity of these compounds was determined. Additionally, the effect of temperature variations upon isomer separations was investigated.     

Subchronic exposure to diflubenzuron causes health disorders in neotropical freshwater fish,Prochilodus lineatus

The action of diflubenzuron (DFB) was evaluated in a freshwater fish, Prochilodus lineatus, after exposure to 0.06, 0.12, 0.25, or 0.50 mg L^?1 DFB for 14 days. Erythrocyte nuclear abnormalities (ENA), the gill activity of Na⁺/K⁺‐ATPase, H⁺‐ATPase and carbonic anhydrase (CA), and lipid peroxidation (LPO) and histopathological changes in the gills and liver were determined. The number of micronuclei increased in fish exposed to 0.25 and 0.50 mg L^?1 DFB. Plasma Cl^? and the CA activity decreased, while the activity of Na⁺/K⁺‐ATPase and of H⁺‐ATPase increased in fish exposed to 0.25 and 0.50 mg L^?1 DFB. LPO did not change in the gills but increased in the liver of fish exposed to 0.25 and 0.50 mg L^?1 DFB. In the gills, histopathological changes indicated disperse lesions and slight to moderate damage in fish exposed to 0.50 mg L^?1 DFB, whereas in the liver, these changes were significantly greater in fish exposed to 0.25 and 0.50 mg L^?1 DFB, indicating moderate to severe damage. Continuous exposure to DFB is potentially toxic to P. lineatus, causing heath disorders when the fish is exposed to the two highest DFB concentrations, which are applied to control parasites in aquaculture and to control mosquito populations in the environment. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 533–542, 2016.     

Simultaneous coprecipitation of lead, cobalt, copper, cadmium, iron and nickel in food samples with zirconium(IV) hydroxide prior to their flame atomic absorption spectrometric determination

A simple and new coprecipitation procedure is developed for the determination of trace quantities of heavy metals (lead, cobalt, copper, cadmium, iron and nickel) in natural water and food samples. Analyte ions were coprecipitated by using zirconium(IV) hydroxide. The determination of metal levels was performed by flame atomic absorption spectrometry (FAAS). The influences of analytical parameters including pH, amount of zirconium(IV), sample volume, etc. were investigated on the recoveries of analyte ions. The effects of possible matrix ions were also examined. The recoveries of the analyte ions were in the range of 95–100%. Preconcentration factor was calculated as 25. The detection limits for the analyte ions based on 3 sigma (n = 21) were in the range of 0.27–2.50 μg L⁻¹. Relative standard deviation was found to be lower than 8%. The validation of the presented coprecipitation procedure was performed by the analysis certified reference materials (GBW 07605 Tea and LGC 6010 Hard drinking water). The procedure was successfully applied to natural waters and food samples like coffee, fish, tobacco, black and green tea.     

Toxicokinetics of glyphosate and its metabolite aminomethyl phosphonic acid in rats

The toxicokinetics of glyphosate after single 100 mg kg⁻¹ intravenous (i.v.) and 400 mg kg⁻¹ oral doses were studied in rats. Serial blood samples were obtained after i.v. and oral administration. Plasma concentrations of glyphosate and its metabolite amiomethyl phosphonic acid (AMPA) were determined by HPLC method. After i.v. and oral administration, plasma concentration–time curves were best described by a two-compartment open model. For glyphosate, the elimination half-lives (T_1/2β) from plasma were 9.99 h after i.v. and 14.38 h after oral administration. The total plasma clearance was not influenced by dose concentration or route and reached a value of 0.995 l h⁻¹ kg⁻¹. After i.v. administration, the apparent volume of distribution in the second compartment (V₂) and volume of distribution at steady state (V_ss) were 2.39 and 2.99 l kg⁻¹, respectively, suggesting a considerable diffusion of the herbicide into tissues. After oral administration, glyphosate was partially and slowly absorbed with a T_max of 5.16 h. The oral bioavailability of glyphosate was found to be 23.21%. Glyphosate was converted to AMPA. The metabolite AMPA represented 6.49% of the parent drug plasma concentrations. The maximum plasma concentrations of glyphosate and AMPA were 4.62 and 0.416 μg ml⁻¹, respectively. The maximum plasma concentration of AMPA was achieved at 2.42 h. For AMPA, the elimination half-life (T_1/2β) was 15.08 h after oral administration of glyphosate parent compound.     

Species-specific responsiveness of four enzymes to endosulfan and predation risk questions their usefulness as general biomarkers

General biochemical biomarkers are widely used in current ecotoxicology and may function as early warning signals. We have, however, poor knowledge on how ecologically similar species differ in their biomarker responsiveness and how predation risk may affect these biomarkers, potentially in an interactive way with pesticides. We evaluated this by exposing four corixid water bug species to combinations of endosulfan and predation risk and quantifying the activity of four general enzymatic biomarkers: acetylcholinesterase (AChE), phenoloxidase (PO), catalase (CAT) and superoxidedismutase (SOD). AChE activity was inhibited at an endosulfan concentration of 2 μg l⁻¹ and this did not differ significantly among species. Predation risk inhibited AChE activity with the same magnitude as endosulfan in one species, S. striata. Reduction in the investment of immune function following pesticide exposure, as measured by the activity of PO, was only observed in C. coleoptrata at 8 μg l⁻¹ while we observed an increase of PO levels in S. striata. Overall, PO was suppressed under predation risk at 8 μg l⁻¹ endosulfan. For SOD we observed a pesticide-induced increase across all species under predation risk, while for CAT the pesticide-induced increase was only present without predation risk. These results indicate that even within this group of ecologically similar and closely related species opposing biomarker responses may exist, as observed for PO. Effects of predation risk on all four enzymes, at a similar magnitude as the pesticide effects, further question their usefulness as general biomarkers.     

Pharmacokinetics of thrombin-like enzyme from venom of Agkistrodon halys ussuriensis Emelianov determined by ELISA in the rat

A thrombin-like enzyme (TLE) was separated and purified from the venom of a northeast Chinese snake Agkistrodon halys ussuriensis Emelianov. Experiments were performed in rats to determine the pharmacokinetic parameters following an intravenous (i.v.) or a subcutaneous (s.c.) injection of the thrombin-like enzyme. The plasma levels of TLE were estimated by enzyme-linked immunosorbent assay. The method exhibited high reproducibility and accuracy in correlating optical densities with TLE concentrations (0.2–30 ng ml⁻¹, r=0.99). The plasma concentration-time course after i.v. administration of 50 μg kg⁻¹ TLE was well fitted by a two-compartment open model. The half-life of the α-phase was 18.0±3.2 min, and that of the β-phase 3.9±0.7 h. The apparent volume of distribution was 1.8±0.5 l kg⁻¹, and clearance was 5.4±0.5 ml min⁻¹ kg⁻¹. When the TLE was injected s.c. at a dose of 0.75 mg kg⁻¹, the changes in plasma concentration were best described by a two-compartment model with a first-order absorption. The maximal plasma level of 51±2.7 ng ml⁻¹ was reached at 5.2±0.5 h. The absorption rate constant was 0.3±0.03 h⁻¹. The area under the plasma concentration-time curve (AUC) was 2.8±0.8 μg h⁻¹ ml⁻¹.     

Oxidative stress responses in gills of goldfish,Carassius auratus,exposed to the metribuzin-containing herbicide Sencor

Metribuzin belongs to the family of asymmetrical triazine compounds and is an active ingredient in many commercial herbicides including Sencor. Effects on goldfish (Carassius auratus L.) of exposure for 96 h to 7.14, 35.7 or 71.4 mg L⁻¹ Sencor 70 WG (corresponding to 5, 25 and 50 mg L⁻¹ of metribuzin) were examined by evaluating oxidative stress markers and activities of antioxidant and associated enzymes in gills. Fish exposed to the lowest Sencor concentration (7.14 mg L⁻¹) showed a 94% increase in levels of protein carbonyls in gills as well as 45% and 144% increases in the activities of glutathione peroxidase and glutathione-S-transferase. Exposure to the highest Sencor concentration (71.4 mg L⁻¹) resulted in reduced levels of protein carbonyls by 56% and lipid peroxides by 40%, as compared with controls, but enhanced levels of low and high molecular mass thiols by 71% and 36%, respectively. The activities of superoxide dismutase, glutathione peroxidase and glutathione-S-transferase were increased in gills of goldfish exposed to 71.4 mg L⁻¹ Sencor. At any concentration tested, Sencor did not affect the activities of glutathione reductase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase or acetylcholine esterase in gills. The results of this study indicate that acute exposure of goldfish to Sencor had effect on free radical processes in gills and glutathione-dependent antioxidants effectively protect proteins and lipids from oxidation.     

Study of forced degradation behavior of Eletriptan hydrobromide by LC and LC–MS and development of stability-indicating method

The objective of the present study was to report the stability profile of novel antimigrain drug Eletriptan hydrobromide based on the information obtained from forced degradation studies. The drug was subjected to acid (0.1–1 mol L⁻¹ HCl), neutral and base (0.1–1 mol L⁻¹ NaOH) hydrolysis and to oxidative decomposition (3–15% (v/v) H₂O₂). Photolysis and thermo degradation at 75 °C were carried out in methanol solution and in solid state with both Eletriptan hydrobromide bulk drug and the tablet formulation. The products formed under different stress conditions were investigated by LC and LC–MS.The experimental conditions for LC were chosen by employing experimental design and multicriteria decision making methodology. These powerful tools enabled the accomplishment of satisfactory resolution with the shortest possible analysis time. Analytes were separated on a C₁₈ column (XTerra™, 150 mm × 3.9 mm, 5 μm) with the mobile phase composed of methanol–water solution of TEA (pH 6.52, 1%, v/v) (30:70, v/v) pumped at 1 mL min⁻¹ flow rate. The column temperature was set at 50 °C and the detection at 225 nm using DAD detector. The LC method was suitably modified for LC–MS analysis which was further used to characterize the arisen degradation products. The possible degradation pathway was outlined based on the results.The drug appeared to be instable towards every stress condition but oxidation. The stability was not jeopardized even under more exaggerated conditions such as increased temperature of the solutions to 75 °C, increased strength of acid/alkali solutions and prolonged testing period.Validation of the LC-DAD method was carried out in accordance with ICH guideline. The method met all required criteria and was applied when testing the commercially available tablets.     

Differential responses to copper-induced oxidative stress in the marine macroalgae Lessonia nigrescens and Scytosiphon lomentaria (Phaeophyceae)

In order to help explain the absence of the brown kelp Lessonia nigrescens from a coastal environment chronically enriched with copper, we characterized the biochemical responses induced by copper stress in this kelp and compared them with those displayed by the copper tolerant brown alga Scytosiphon lomentaria. These algae were cultivated with increasing concentrations of copper (20, 40 and 100 μg L⁻¹) for 96 h and the temporal production of hydrogen peroxide, superoxide anions and lipoperoxides as well as the activities of antioxidant enzymes catalase (CAT), glutathione peroxidase (GP), ascorbate peroxidase (AP), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) and the activity of the defense enzyme lipoxygenase (LOX) were determined. In L. nigrescens and S. lomentaria, a single peak of hydrogen peroxide was detected, with similar maxima after 3 h of copper exposure, although in L. nigrescens buffering took longer. Superoxide anions, on the other hand, were only detected in L. nigrescens. The production of lipoperoxides in L. nigrescens increased steadily at higher copper levels, in a pattern clearly different to their rapid stabilization in S. lomentaria. We suggest that the accumulation of lipoperoxides might be related to LOX, whose activity also increases with exposure time. Furthermore, activities of the antioxidant enzymes CAT, GP, AP and DHAR were lower in L. nigrescens than in S. lomentaria, and GP and DHAR were completely inhibited at higher copper concentrations. Since these enzymes also detoxify fatty acid hydroperoxides, their inhibition, together with the activation of LOX, may explain the persistent and copper-dependent levels of lipoperoxides in L. nigrescens. Based on terrestrial plant models demonstrating toxic effects of lipoperoxides, and on our results on organellar ultrastructural changes, we suggest that copper toxicity induced an uncontrolled lipoperoxide accumulation which may lead to cell damage and dysfunction in L. nigrescens, explaining at least partially, the absence of this kelp in a copper-enriched coastal environment.     

A stability-indicating HPLC assay with diode array detection for the determination of a benzylpenicillin prodrug in aqueous solutions

The aim of this study was to develop a stability-indicating HPLC assay for the determination of penethamate (PNT), an ester prodrug of benzylpenicillin (BP), in aqueous solutions. The method was validated by subjecting PNT to forced decomposition under stress conditions of acid, alkali, water hydrolysis and oxidation. A quenching solution was developed to limit degradation to negligible levels before and during the analysis. Both PNT and BP were simultaneously determined and separated in presence of degradation products on a C₁₈ column using a mobile phase consisting of methanol–acetonitrile–acetate buffer. Different degradation products were formed in the stress conditions. The peak purity indexes of PNT and BP obtained by diode array detection were >0.999, confirming the absence of other co-eluting substances. The assay was linear for both analytes in the concentration range 1–100 μg mL⁻¹. The LOD and LOQ of PNT were 0.03 and 0.09 μg mL⁻¹ respectively. Degradation of PNT followed pseudo-first-order kinetics with t_1/2 of 43.6 min at pH 2.01 and 4.2 min at pH 9.31. In addition, the absence of BP in the acidic solutions of PNT emphasises the futility of monitoring BP to assess the stability of PNT. In conclusion, the assay is rapid and stability-indicating with adequate precision and accuracy, and in conjunction with the quenching solution, can be used for stability studies of PNT with simultaneous quantitation of BP. The degradation studies provide useful information for formulation development of PNT.     

Quantitation of acetazolamide in rat plasma, brain tissue and cerebrospinal fluid by high-performance liquid chromatography

A simple and sensitive high-performance liquid chromatographic method for the analysis of acetazolamide (AZ) in rat blood (plasma/serum, whole blood and serum ultrafiltrate), brain tissue and cerebrospinal fluid (CSF) was described. Quantitative extraction of AZ with ethyl acetate from both buffered plasma and brain tissue homogenate (pH 8.0) was achieved. Each extract was evaporated to dryness and the residue was chromatographed on a reversed-phase column. CSF was directly analysed without extraction step. The limits of detection were 0.05 μg ml⁻¹ for plasma, 0.02 μg g⁻¹ for brain tissue and 0.004 μg ml⁻¹ for CSF. Calibration curves were linear over the working ranges of 0.1–100 μg ml⁻¹ for plasma, 0.05–50 μg g⁻¹ for brain tissue and 0.025–50 μg ml⁻¹ for CSF. The reproducibility of AZ assay in the rat biologic media indicated very low relative standard deviations (RSDs). The recoveries of AZ added to plasma and brain tissue were more than 96% with an RSD of less than 5%. The present method was applied to studies of plasma concentration profiles of the drug after administration and its distribution into central nervous system.     

3-iodothyroacetic acid,a metabolite of thyroid hormone,induces itch and reduces threshold to noxious and to painful heat stimuli in mice

Background and purpose

Itch is associated with increased sensitization to nociceptive stimuli. We investigated whether 3-iodothyroacetic acid (TA1), by releasing histamine, induces itch and increases sensitization to noxious and painful heat stimuli.

Experimental Approach

Itch was evaluated after s.c. administration of TA1 (0.4, 1.32 and 4 μg·kg⁻¹). Mice threshold to noxious (NHT) and to painful heat stimuli were evaluated by the increasing-temperature hot plate (from 45.5 to 49.5°C) or by the hot plate (51.5°C) test, respectively, 15 min after i.p. injection of TA1 (0.4, 1.32 and 4 μg·kg⁻¹). Itch, NHT and pain threshold evaluation were repeated in mice pretreated with pyrilamine. Itch and NHT were also measured in HDC^+/+ and HDC^−/− following injection of saline or TA1 (1.32, 4 and 11 μg·kg⁻¹; s.c. and i.p.). pERK1/2 levels were determined by Western blot in dorsal root ganglia (DRG) isolated from CD1 mice 15 min after they received (i.p.): saline, saline and noxious heat stimulus (46.5°C), TA1 (0.1, 0.4, 1.32, 4 μg·kg⁻¹) or TA1 1.32 μg·kg⁻¹ and noxious heat stimulus.

Key Results

TA1 0.4 and 1.32 μg·kg⁻¹ induced itch and reduced NHT; pyrilamine pretreatment prevented both of these effects. TA1 4 μg·kg⁻¹ (i.p.) reduced pain threshold without inducing itch or modifying NHT. In HDC^−/− mice, TA1 failed to induce itch and to reduce NHT. In DRG, pERK1/2 levels were significantly increased by noxious heat stimuli and by TA1 0.1, 0.4 and 1.32 μg·kg⁻¹; i.p.

Conclusions and Implications

Increased TA1 levels induce itch and an enhanced sensitivity to noxious heat stimuli suggesting that TA1 might represent a potential cause of itch in thyroid diseases.