Analgesic Effects of Tetrodotoxin Combined with Acetylsalicylic Acid on Acetic Acid-induced Abdominal Constriction and Formalin Test in Mice

Aim To study the effects of tetrodotoxin （TTX） combined with acetylsalicylic acid （ASA） on nociceptive stimulus in mice. Methods To assess the antinociceptive effects of TTX, ASA or TTX plus ASA, the acetic acid-induced abdominal constriction test and formalin pain test were used. Results TTX （0.5 - 4.0 μg· kg^-1 ） or ASA （25 - 200 mg· kg^-1 ） im produced a significant inhibition of acetic acid-induced abdominal constriction. The median inhibitory doses （ID508） were 2.1 μg· kg^-1 for TTX（ and 64 mg· kg^-1 for ASA. TTX and ASA also showed a dose-dependent inhibition of the second phase response in the formalin pain model, the ID508, being 2.3μg·kg^-1 and 74.2 mg· kg^-1, respectively. The ihteraction between TTX and ASA was synergistic, as evidenced by the fact that （1） when ASA alone compared with the combination of TTX （0.79 μg · kg^-1 or 0.39μg· kg^-1 ） and ASA, the ID508, of ASA reduced from 64.0 mg· kg^-1 to 5.8 mg· kg^-1 or 12.6 mg· kg^-1, and from 74.2 mg· kg^-1 to 7.4 mg· kg^-1 or 13.0 mg· kg^-1 on tile two models of nociceptive tests, respectively; and that （2） synergism in the analgesic effects was shown by isobiolographic analysis. Conclusion TTX, ASA and the combination of the two drags produce analgesic effects in acetic acid-induced abdominal constriction test and formalin-induced pain test. The interactions between TTX and ASA may be useful in developing novel analgesic agents.

外周formalin刺激时大鼠脊髓灰质神经元c-Fos蛋白和NMDA受体的双标记免疫细胞化学研究(英文)

利用免疫细胞化学双标技术，研究了大鼠后脚掌注入ｆｏｒｍａｌｉｎ时脊髓ｃ－Ｆｏｓ蛋白和ＮＭＤＡ受体在脊髓灰质不同层次神经元的分布。结果表明，脊髓背角Ⅰ－Ⅱ层、Ⅴ－Ⅵ层、和Ｘ层中的Ｆｏｓ样免疫反应阳性神经元中分别有２８．６％，５８．１％和６４．８％呈现ＮＭＤＡ受体样免疫反应阳性。此结果提示长时间的外周伤害性刺激作用时，脊髓不同层次的伤害性感受神经元可能由于ＮＭＤＡ受体分布的不同而在持续痛刺激过程中起着不同的作用。

^1HNMR方法研究以DMSD6为溶剂高醇Formalin溶液

用1 HNMR方法研究了工业高醇formalin溶液体系 ,发现以DMSD6 (氘代二甲基亚砜 )为溶剂的1 HNMR谱图中 ,溶剂与样品的不同配比 ,使谱图发生明显变异 ,这与通常NMR能得到确定的试样谱图不同。通过对formalin溶液体系的分析 。

激活外周第三组mGluRs抑制Formalin诱导的大鼠脊髓p38MAPK的活化

目的:观察脚掌皮下注射第三组代谢型谷氨酸受体(mGluRs)激动剂L-SOP对福尔马林(Formalin)炎性痛大鼠脊髓有丝分裂原激活蛋白激酶p38族(p38MAPK)活化的影响。方法:雄性Wistar大鼠48只,随机分为4组(n=12):分别为对照组即生理盐水组和三个不同剂量的L-SOP实验组,每组6只测定痛行为反应,另外6只测定p38MAPK的含量及活化情况。结果:与对照组比较,三个实验组大鼠第二时相的痛行为反应明显被抑制,12.5mmol/L组与25 mmol/L组还观察到大鼠第一时相的痛行为反应亦受到抑制;此外,12.5 mmol/L组与25 mmol/L组脊髓p38MAPK的活化水平与对照组比较明显下降。结论:外周L-SOP能抑制痛行为反应及降低脊髓p38MAPK的活化水平,提示外周组织中有功能性第三组代谢型谷氨酸受体的表达并参与外周痛感受器对伤害性信息的处理。

Formalin fixation on HER-2 and PD-L1 expression in gastric cancer:A pilot analysis using the same surgical specimens with different fixation times

BACKGROUND The needs for human epidermal growth factor receptor 2(HER-2) and/or programmed death-ligand 1(PD-L1) evaluations in gastric cancer are dramatically increasing. Although the importance of standardization of sample fixation has been widely recognized, most of the evidence regarding the fixation duration or type of fixing solution are based on breast cancer.AIM To investigate the real effects of fixation conditions on HER-2 testing or PD-L1 testing for gastric cancer using gastrectomy specimens.METHODS Thirty-two patients who underwent gastrectomy for gastric cancer were enrolled.Their resected specimens were each divided into four pieces and fixed in four strictly controlled different durations(6 h, 24 h, and 48 h, and 1 wk) by 10%formalin(n = 22) or 10% neutral buffered formalin(NBF)(n = 10).Immunohistochemistry(IHC) of HER-2 and PD-1 was performed, and a pathology examination was conducted. In the HER-2-immunoreactive cases, all four specimens were subjected to dual-color in situ hybridization(DISH). Five cases were assessed as HER-2-positive by IHC and DISH. We used the cut-off values of 1%, 10%, and 50% to assess the IHC findings of PD-L1.RESULTS No significant difference was observed in comparisons between the shorter fixation period groups(6 h, 24 h, and 48 h) and the prolonged fixation period(1 wk) group in the HER-2 and PD-L1 analyses. Although no significant difference was observed between 10% formalin and 10% NBF within 1 wk of fixation, the superiority of 10% NBF was confirmed in a long-term(> 3 mo) fixation in both the HER-2 and PD-L1 analyses.CONCLUSION In this small-numbered pilot study, prolonged fixation within 1 wk showed no inferiority in HER-2 or PD-L1 testing. However, a large-numbered prospective study is needed to obtain conclusive results.

Treatment of hemorrhagic radiation-induced proctopathy with a 4% formalin application under perianal anesthetic infiltration

AIM:To evaluate the results of hemorrhagic radiation proctopathy treatment with a 4% formalin application.METHODS:A prospective study was performed.Over a three-year period,38 patients underwent 4% formalin application under perianal anesthetic infiltration for hemorrhagic radiation proctopathy.All patients included in the study were irradiated for prostate cancer.The patients ranged in age from 56-77 years(average 70 ± 5 years).All of the patients were referred for formalin therapy after noninvasive management had failed.Twenty-four(63.2%)patients underwent a single application,10(26.3%)patients underwent 2 applications,and 4(10.5%)patients underwent 3 applications.RESULTS:Two to 36 mo(average 12 ± 3 mo)following treatment,34 patients were interviewed(four were lost to follow-up).Twenty(58.8%)subjects reported complete cure,8(23.5%)subjects reported significant improvement,and 6(17.7%)subjects reported no change.One patient(who underwent a colostomy at a regional hospital with no specialized services available for previous bleeding episodes from radiation proctopathy)was cured,and the colostomy was closed.One patient(2.6%)developed rectal mucosal damage after the second application.CONCLUSION:A 4-min application of 4% formalin for hemorrhagic radiation-induced proctopathy under perianal anesthetic infiltration in patients who have received external radial radiation therapy for prostate cancer is simple,reasonably safe,inexpensive,generally well tolerated,and effective.

DNA Extraction from Formalin Fixed <i>Coilia macrognathos</i>Fin Tissues

Approximately 200 mg of fin tissue from each specimen was cut into pieces and treated with a gradient of ethanol (65%, 70%, 75%, 80%, 85%, 90%, 95% and 100%) and then DNA was extracted from formalin fish fin tissues. Agarose gel visualization of the DNA confirmed DNA extracted. MtDNA cyt b gene banding pattern of samples with agarose gel was clearly visible and could be used to be sequenced. In terms of DNA purity, the 260/280 ratio of 87.5% samples ranged between 1.8 and 2.0, indicating that DNA of the majority of the samples was pure. The developed DNA extraction procedure from formalin fish fin tissues by pretreatment with a gradient of ethanol system will be a useful tool to study the genetic structure and phylogenesis of endangered fish, by specimens preserved formalin-fixed in museum and herbarium.

鞘内注射氯胺酮/吗啡对大鼠Formalin炎性痛的影响

目的:观察鞘内注射氯胺酮/吗啡对大鼠Formalin炎性痛行为学的影响。方法:雄性Wistar大鼠24只,随机分为4组,分别为生理盐水组、吗啡组、氯胺酮组和吗啡+氯胺酮组,观察大鼠的痛行为反应。结果:与生理盐水组比较,其余三组大鼠痛行为反应均被明显抑制,P<0.05。结论:在大鼠Formalin炎性痛模型中,吗啡和氯胺酮可以明显抑制大鼠痛行为反应,吗啡和氯胺酮有协同作用。

Effects of Lugol's iodine solution and formalin on cell volume of three bloom-forming dinoflagellates

Fixatives are traditionally used in marine ecosystem research. The bias introduced by fixatives on.the dimensions of plankton cells may lead to an overestimation or underestimation of the carbon biomass. To determine the impact of traditional fixatives on dinoflagellates during short- and long-term fixation, we analyzed the degree of change in three bloom-forming dinoflagellates （Prorocentrum rnicans, Scrippsiella trochoidea and Nocfiluca scintillans） brought about by Lugol＇s iodine solution （hereafter Lugol＇s） and formalin. The fixation effects were species-specific. P. micans cell volume showed no significant change following long-term preservation, and S. trochoidea swelled by approximately 8.06% in Lugol＇s and by 20.97% in formalin as a percentage of the live cell volume, respectively. N. scintillans shrank significantly in both fixatives. The volume change due to formalin in N. scintillans was not concentration-dependent, whereas the volume shrinkage ofN. scintillans cells fixed with Lugol＇s at a concentration of 2% was nearly six-fold that in cells fixed with Lugol＇s at a concentration of 0.6%-0.8%. To better estimate the volume of N. scintillans fixed in formalin at a concentration of 5%, we suggest that the conversion relationship was as follows： volume of live cell=volume of intact fixed cell/0.61. Apart from size change, damage induced by fixatives on N. scintillans was obvious. Lugol＇s is not a suitable fixative for N. scintillans due to high frequency of broken cells. Accurate carbon biomass estimate ofN. scintillans should be performed on live samples. These findings help to improve the estimate of phytoplankton cell volume and carbon biomass in marine ecosystem.

Acute Toxicities of Potassium Permanganate, Formalin, and Lugol's Iodine Solution to a Marine Ciliate, Pleuronema coronatum (Ciliophora, Scuticociliatida)

Acute toxicities of potassium permanganate, formalin, and Lugol’s iodine solution to a commonly occurred marine ciliate Pleuronema coronatum (Ciliophora, Scuticociliatida) were measured. Linear regression analysis of the results highlighted the close relationships between doses of the medicines and mortalities of the organisms, thus providing a capability to predict toxicity effects from the dose. Toxic effects of the medicines on the ciliates were described in the present paper, and the median lethal concentrations (LC 50 values) were given. Results of measurements indicated that 2 h-LC 50 and 12 h-LC 50 values of formalin on P. coronatum were 59.00×10 -6 and 43.57×10 -6, while those of Lugol’s solutions were 90.13 and 67.84×10 -6 respectively. The tolerance of P. coronatum to formalin is apparently lower than that to Lugol’s iodine solution and potassium permanganate is a suitable medicine to kill ciliates in short time.

DNA Extraction from Formalin-fixed and Paraffin-embedded Tissues by Triton X-100 for Effective Amplification of EGFR Gene by Polymerase Chain Reaction

For first-line non-small-cell lung cancer（NSCLC） therapy,detecting mutation status of the epidermal growth factor receptor（EGFR） gene constitutes a prudent test to identify patients who are most likely to benefit from EGFR-tyrosine kinase inhibitor（TKI） therapy.Now,the material for detecting EGFR gene mutation status mainly comes from formalin-fixed and paraffin-embedded（FFPE） tissues.DNA extraction from FFPE and the amplification of EGFR gene by polymerase chain reaction（PCR） are two key steps for detecting EGFR gene mutation.We showed a simple method of DNA extraction from FFPE tissues for the effective amplification of EGFR gene.Extracting DNA from the FFPE tissues of NSCLC patients with 1% Triton X-100（pH=10.0） was performed by heating at 95 °C for 30 min.Meanwhile,a commercial kit was used to extract DNA from the same FFPE tissues of NSCLC patients for comparison.DNA extracted products were used as template for amplifying the exons 18,19,20 and 21 of EGFR by PCR for different amplified fragments.Results show that DNA fragment size extracted from FFPE tissues with 1% Triton X was about 250―500 base pairs（bp）.However,DNA fragment size extracted from FFPE tissues via commercial kit was about from several hundreds to several thousands bp.The DNA yield extracted from FFPE tissues with 1% Triton X was larger than that via commercial kit.For about 500 bp fragment,four exons of EGFR could not be amplified more efficiently from extracted DNA with 1% Triton X than with commercial kit.However,for about 200 bp fragment.This simple and non-laborious protocol could successfully be used to extract DNA from FFPE tissue for the amplification of EGFR gene by PCR,further screening of EGFR gene mutation and facilitating the molecular analysis of a large number of FFPE tissues from NSCLC patients.

Effects of Extremely Low Frequency Magnetic Field (ELF-MF) on Formalin Induced Chronic Pain in Mice

Background: Effects of Extremely Low Frequency Magnetic Field) ELF-MF (in the elevation of blood sugar, cholesterol, triglyceride and reduction of withdrawal syndrome of morphine have been reported so far. Since pain is one of the main concerns in medicine and usually analgesic drugs are not much beneficial or cause considerable side effects, the present project was carried out with the aim of evaluating the effects of (ELF-MF (in chronic pain using formalin test in mice. Materials & Methods: In this experimental study, thirty two adult male mice were used and divided into 4 groups (n = 8). Three groups of animals exposed daily for thirty minutes to 25, 50, 75 HZ (intense 250 μT) of electromagnet field for one week, respectively and one group considered as control with no exposure. At the end of a week, formalin test was performed. Responses to formalin were observed for sixty minutes. The results were compared between tests and control group. Findings: In acute phase of formalin test, ELF-MF reduced significantly the pain scores following formalin injection at all 3 frequencies, especially at 25 and 50 HZ (p < 0.001) rather 75 HZ (p < 0.05). In chronic phase of formalin test, ELF-MF reduced pain scores at 25 and 50 HZ (p < 0.05). However, the most effective responses were obtained at 50 HZ frequency. Conclusion: The findings show that ELF-MF is effective to reduce formalin induced chronic pain in mice at both acute and chronic phases.

Intradermal administration of formalin to the cheek induces itch as well as pain behaviors in rats

Objective · Formalin is a classic and most widely used algogenic substance, but its itchy effect is not clear. The present study aims to explore the hypothesis that formalin may induce itch as well as pain. Methods · Flinching, as well as licking and forelimb wiping of the site of injection were counted as pain responses, whereas biting and hind paw scratching of the cheek were counted as itchy responses. To discriminate formalin-induced sensations in rats, the irritant(saline as control) was injected, and then pain and itchy responses were recorded.Results · Intraplantar injection of formalin elicited biphasic behavior responses characterized as flinching, as well as biting or licking of the hind paw without significant gender differences. Following intradermal administration of formalin to the cheek, rats exhibited episodic forelimb wiping of the cheek, representative of pain. No gender difference was noticed for this type of behavior. In addition, episodes of hind paw scratches of the cheek, representative of pruritoceptive responses, also occurred. Interestingly, hind paw scratches appeared to be more pronounced in male than in female rats. Conclusion · Intradermal administration of formalin elicits pruritoceptive as well as nociceptive responses in rats.

Intrathecal MK-801 inhibits formalin-induced activation of spinal p38-MAPK in rats

BACKGROUND： p38 mitogen-activated protein kinase （MAPK） plays an instrumental role in signal transduction from the cell surface to the nucleus, while subcutaneous injection of formalin can induce increased activation of spinal p38 MAPK. However, the mechanisms underlying the formalin-induced activation of spinal p38 MAPK in rats are unclear. OBJECTIVE： To observe the effects of N-methyl-D-aspartic acid （NMDA） receptor antagonist MK-801 on the formalin-induced activation of spinal p38 MAPK in rats. DESIGN, TIME AND SETTING： This randomized grouping, controlled animal experiment was performed at the Department of Physiology and Neurobiology, Shanxi Medical University between May and November 2007. MATERIALS： Forty eight healthy, adult Wistar rats were randomly divided into two groups： formalin ＋ normal saline （n = 12） and formalin ＋ MK-801 （n = 36）. The formalin ＋ MK-801 group was further divided into three subgroups according to the dosage of MK-801 （10, 50, and 100 nmol/L, 12 rats for each subgroup） METHODS： Following anesthesia, polyethylene tubing filled with sterile normal saline was implanted into the subarachnoid cavity. On postoperative days 5-8, rats received a 15 minute perfusion of normal saline or MK-801 （10, 50, and 100 nmol/L） in the formalin ＋ normal saline and formalin ＋ MK-801 groups, respectively, followed by formalin injection for the induction of nociceptive behavior. MAIN OUTCOME MEASURES： Detection of total p38 MAPK and of phosphorylated p38 MAPK by western Blot analysis; observation of nociceptive behaviors in the 1 hour after formalin injection. RESULTS： Western Blot analysis revealed that injection of formalin had no effect on total p38 MAPK expression but resulted in increased phosphorylation of p38 MAPK in the spinal cord. This increase was apparent after 5 minutes, peaked at 20 minutes, and thereafter descended and reached control levels after 45 minutes. Pretreatment with MK-801 （10, 50, 100 nmol/L） resulted in a dose-dependent reduction of p38 MAPK phosphorylation in the spinal cord, 20 minutes after formalin injection. Injection of 50 and 100 nmol/L MK-801 produced a suppression of the first phase of nociceptive behaviors, and all three doses of MK-801 resulted in dose-dependent inhibition of the second phase of nociceptive behaviors. CONCLUSION： The NMDA receptor participates in formalin-induced activation of p38 MAPK in the rat spinal cord.

Acute Toxicity of Formalin to the Red-tide Dinoflagellate Prorocentrum minimum Schiller(Protozoa,Mastigophora)

The acute toxic levels of formalin to a marine red-tide dinoflagellate Prorocentrum minimum Schiller (Mastigophora, Dinoflagellida) were determined by linear regression analysis. The data obtained revealed that there is a close regression relationship between logarithmic concentrations of formalin and mortality probit scales of the organism when exposure times are 1, 2, 6, 12, 24h. The median lethal concentrations (LC50 values) obtained from correlation analysis for these exposure times (with 95% confidence intervals), were 11.83, 6.76, 4.37, 4.27 and 3.98mgL-1, respectively. A toxicity curve was obtained to connect the exposure time and LC50 value from the correlation between them. The results indicated that P. minimum could be killed or fixed by formalin in the concentration range of 4-12mgL-1 within 1-24h.

A Comparative Study of Present Status of Marketing of Formalin Treated Fishes in Six Districts of Bangladesh

The fish is an important food stuff and source of protein all over the world. In Bangladesh, fisheries sector contributes a lot, in the case of the earning foreign currency and meeting domestic need of the animal proteins. To fulfill the domestic need of protein and fish, Bangladesh imports fish and fish products from the neighboring county. In many studies, it was proved that most of the imported fishes are contaminated with formalin, which is the highly hazardous and carcinogenic chemical. Information was collected from the fish retailers and consumers on the marketing of the formalin treated fishes through survey using prescribed questionnaire at 18 different fish markets in 6 different districts of Bangladesh. It was found that most of the commercially imported fishes are highly contaminated with formalin. On the other hand, local big fishes, such as rui (Lobeo Rohita), catla (Catla catla) and mrigal (Cirrhinus cirrhosus) etc., are also formalin contaminated partially, but not all the fishes. All the local small fishes are free from the formalin contamination. In this study, it was found that, among the 939 fish samples collected from the different fish markets of the six districts, 213 fishes (22.68%) were directly contaminated with formalin. The contamination rate is so much higher in the big city like Dhaka (36.78%) and lower in the small town like Jamalpur districts (13.33%). This study also indicated that, all the village markets were totally free from the formalin contamination. As the fish traders used formalin to increase the shelf life of the fishes, it was also observed that, the shelf life of the local fishes or formalin free fishes was much higher and the organoleptic characteristics were much more excellent than the formalin contaminated local or imported fishes. The price of the imported fishes was also lower than the local fishes. It was also clear that, the organoleptic characteristics of the imported fishes and formalin contaminated fishes were greatly different than the local fishes, which were not satisfactory to the consumers. The study also indicated that, the overall hygienic practice and sanitary conditions of the markets and the fish traders/retailers were very poor, not satisfactory. This survey also revealed that, all the traders or retailers who were mixed formalin with the fishes, knew about the bad effects of the formalin.

Formalin Contaminated in Seafood and Frozen Meat at Somdet Market, Kalasin Province

Formaldehyde or formalin is highly toxic that is absorbed pleasantly by inhalation. The object of this research was to analyze formalin that contaminated in seafood and frozen meat. The method was to select samples at Kalasin Province. The samples were mackerel, crisp squid, frozen chicken, Saba fish, Shishamo fish, Jelly fish, Cockle, Clams, Squid, shrimp, White shrimp and Dolly fish, respectively. The methods were to analyze formaldehyde with titration and formalin test kit. Titration method used formic acid by excess of iodine in alkaline solution. Formalin test kit?of Ministry of Public Health issued Act No.151 (B.E.2536) was to test formalin contaminated food.?The results found formaldehyde in mackerel, crisp squid, frozen chicken, Saba fish, Shishamo fish, jelly fish, cockle, clams, squid, shrimp, white shrimp and dolly fish in three replicated were 288 mg/L, 228 mg/L, 293 mg/L, 77 mg/L, 282 mg/L, 180 mg/L, 120 mg/L, 48 mg/L, 229 mg/L, 294 mg/L, 295 mg/L and 293 mg/L, respectively. Formalin test kit was to found all samples were contaminated with formalin. Moreover, the height formalin contaminated in white shrimp, the second were shrimp and dolly fish, the third was frozen chicken, the fourth was mackerel, the fifth was Shishamo fish, the sixth was squid, the seventh was crisp squid, the eighth was jelly fish, the ninth was cockle, the tenth was Saba fish and the last was clam. The World Health Organization classified formaldehyde was carcinogenic to humans, considerately that there was a decent proof for inflicting cavity cancer in humans.

Trefoil Factor 3 (TFF3) mRNA Expression Level in Follicular Thyroid Tumors Using Formalin-Fixed, Paraffin-Embedded (FFPE) Blocks

Background: Differential diagnosis of follicular thyroid carcinoma (FTC) from follicular thyroid adenoma (FTA) is often difficult since presence or absence of capsular/vascular invasion can not be determined by preoperative fine needle aspiration cytology, and may not be judged unanimously on permanent sections even among experienced pathologists. Determination of molecular-genetic factors such as trefoil factor 3 (TFF3) mRNA in the follicular thyroid tumors may be useful aid to improve the accuracy of diagnosis, though it is considered to be unstable and relatively low concentrated genetic substance. Purpose of our study is to investigate expression level of TFF3 mRNA of thyroid follicular tumors using formalin-fixed, paraffin-embedded (FFPE) tissue. Methods: Study population included FFPE sections from 19 FTC cases, 20 FTA cases, 11 adenomatous goiter (G) cases and 12 samples of normal thyroid tissue (N) adjacent to thyroid tumors. RNeasy FFPE kit was used for extraction of total RNA. Purification and concentration values were determined by spectrophotometer. Extracted RNA was used for cDNA synthesis in reverse transcription. Synthesized cDNA subsequently proceeded for relative quantification of TFF3 mRNA by RT-qPCR using TFF3 primers. Glyceroldehyde-3-phosphate dehydrogenase (GAPDH) and hypoxanthin phosphorobosyltransferase1 (HPRT1) were used as control genes. The mean and standard deviation of TFF3 mRNA expression level were analyzed by software Multiplate RQ. Results: Extraction by the FFPE kit yielded high concentration of RNA in all cases. Purification values were 1.8 in average. Concentration values were significantly higher in FTC and FTA relative to G and N tissues, possibly due to high density of thyrocytes in the samples. Relative quantification of TFF3 mRNA expression level showed broad ranges both in FTC and FTA, while the analyses in G and N tissues indicated narrow ranges. Conclusion: FFPE tissues from thyroid follicular tumors can be used for measurement of unstable and low concentrated genetic substances such as TFF3 mRNA. Its diagnostic value yet remains to be determined.

Effects of multiple intrathecal administration of L-arginine with different doses on formalin-induced nociceptive behavioral responses in rats

Objective To investigate the effects of nitric oxide （NO） with different doses on modulation of inflammatory pain, and its possible mechanisms.Methods NO precursor L-arginine （L-Arg） was intrathecally administered in rats at a dose of 10 μg per day （low dose group） or 250μg per day （high dose group） for a succession of 4 d.Normal saline was applied as a control.Then the rats were subcutaneously injected with formalin （100μL,2%） into the right hindpaw,and the nociceptive behavioral responses within 1 h were observed.At 4 h after formalin injection,neuronal NO synthase （nNOS） and c-Fos expression in spinal dorsal horn was examined with immunocytochemistry method.Results The subcutaneous injection of formalin evoked biphasic behaviors of licking or biting the injected paw.There was no difference in acute phase of formalin test among the 3 groups,while in tonic phase,the licking and biting time,and the protein levels of nNOS and c-Fos in spinal dorsal horn were significantly decreased in low dose group and increased in high dose group,compared with those in control group.Conclusion These results suggest that multiple administration of NO with different doses may produce different effects.On one hand,the low dose of NO can induce antinociception.On the other hand,the high dose of NO can induce pronociception.

Peripheral Leptin Signaling Mediates Formalin-Induced Nociception

Accumulating evidence suggests that obesity is associated with chronic pain. However, whether obesity is associated with acute inflammatory pain is unknown. Using a well-established obese mouse model induced by a highfat diet, we found that:(1) the acute thermal pain sensory threshold did not change in obese mice;(2) the model obese mice had fewer nociceptive responses in formalininduced inflammatory pain tests; restoring the obese mice to a chow diet for three weeks partly recovered their pain sensation;(3) leptin injection induced significant phosphorylation of STAT3 in control mice but not in obese mice,indicating the dysmodulation of topical leptin–leptin receptor signaling in these mice; and(4) leptin–leptin receptor signaling-deficient mice(ob/ob and db/db) or leptin–leptin receptor pathway blockade with a leptin receptor antagonist and the JAK2 inhibitor AG 490 in wildtype mice reduced their nociceptive responses in formalin tests. These results indicate that leptin plays a role in nociception induced by acute inflammation and that interference in the leptin–leptin receptor pathway could be a peripheral target against acute inflammatory pain.