Chronic constriction injury (CCI) is a commonly accepted model of neuropathic pain, which has been introduced by Bennett and Xie in 1988. This model contains the most usual characteristics of human neuropathic pain due to an increase in central sensitization like hyperalgesia and allodynia. It is a usual practice to apply acute pain stimulants such as thermal and mechanical ones for assessment of CCL In this experiment, FORMALIN has been used as a chemical stimulant, which produces two phases of acute and chronic pain. In this way, the effect of CCI is not only determined in the acute phase, but also in the chronic phase, which the latter has a different mechanism of development. Furthermore, the role of FORMALIN pain prior to CCI on FORMALIN pain following CCI was also studied. Moreover, the role of intravenous injection of lidocaine, as a central pain blocker, before injection of FORMALIN prior to CCI and its effect on the FORMALIN pain post CCI was also investigated. The results showed that in the first phase of FORMALIN test, CCI produced hyperalgesia at second day post CCI in the group which had sciatic ligation without FORMALIN injection prior to CCI and hyperalgesia at day 14 post CCI in all groups, with or without FORMALIN injection prior to CCI and the group who had lidocaine. In this respect, there were not any significant changes in the second phase of FORMALIN test in all groups, except for hyperalgesia at second day post CCI in the group which had not received FORMALIN prior to CCI.

Background: FORMALIN is an aqueous solution of formaldehyde. It is a protoplasmic poison and causes coagulation necrosis and tissue fixation.Case: A 19-year-old girl was brought for autopsy to the mortuary of JSS Medical College, Mysore.Conclusion: FORMALIN is an unusual poison to be ingested for suicidal purposes due to selective availability and its strong taste and odor.

Tissue fixation is a vital step in preparation of samples for histological studies and mistakes at this stage could lead to irreversible damage. The aim of this study was to compare the effect of three sample preparation-fixation methods on histomorphometic indices of small intestine of broilers. Thirty 10 day old broilers of Ross 308 strain were used in the study. Segments of small intestine were washed and prepared as opened or closed sections. The closed sections were fixed in 10% saline-FORMALIN. The opened samples were cut at the mesenteric line and were fixed by 10% saline-FORMALIN. In Clarke’ s fixation the ends of samples were sealed by string and Clarke’ s solution was injected into the lumen. Fixed samples were subjected to paraffin embedding and 5 µ m sections were cut using rotary microtome and sections were stained by Eosin-Hematoxylin and Alcian blue. In each section the villus height, villus thickness, crypt depth and goblets’ density were measured under light microscope and the villus surface index was also calculated. Data were subjected to ANOVA in a completely randomized design with three treatments and 30 observations. The results indicated that method of preparation-fixation had a significant effect on morphometric indices (p<0. 01). The closed-FORMALIN’ s samples had the greatest villus height and crypt depth values in all three intestinal segments, while the lowest values were observed in closed-Clarke’ s method (p<0. 01). Closed-Clarke’ s samples had the thickest villus in all three parts of small intestine followed by closed-FORMALIN’ s and opened-FORMALIN’ s samples (p<0. 01). Villus surface area was highest in closed-FORMALIN fixed samples (p<0. 01). Considering simplicity of the method, low cost, better mucosal protection and lack of severe tissue changes observed in closed-FORMALIN’ s method, this method was considered as a method of choice in histomorphometric studies of poultry small intestinal mucosa.

In the present study, the effect of swim stress on morphine-induced tolerance was investigated in mice using FORMALIN test. In this respect, intraperitoneal administration of different doses of morphine (3, 6, and 9 mg/kg) induced a dose-dependent antinociception in both acute and chronic phases of the FORMALIN test. In addition, an exposure to swim stress 2 or 3 times for 3 consecutive days was performed in order to induce tolerance. This exercise decreased morphine-induced antinociception. Meanwhile, morphine administration (25 mg/kg) for 3 days in the presence of swim stress (for two to three times) potentiated tolerance induced by morphine in both phases of the FORMALIN test. Administration of a higher dose of morphine (50 mg/kg) for 3 days in the presence of swim stress did not alter morphine-induced tolerance in both phases of the test. On the other hand, administration of the latter dose of morphine for 3 days in the absence of swim stress decreased morphine-induced antinociception in both phases of the FORMALIN test. It can be concluded that there may be a cross interaction between morphineinduced antinociception and swim stress.

Gossypin is a bioflavonoid isolated from Hibiscus Vitifolus Linn. The antinociception activity of gossypin has been studied in comparison with the standard antinociception agent, morphine, against the experimental model of tonic continuous pain produced by FORMALIN. FORMALIN (0.1ml of 1% solution) was injected under the plantar surface of right hind paw of mice and the time an animal spent in liking the injected paw was measured. Gossypin was administered before the induction of pain by FORMALIN and its effect was measured compare with morphine. The data were analysed. Gossypin has been found to be effective against pain induced by FORMALIN in a dose dependent manner. The antinociception activity of gossypin has been studied in comparison with the standard antinociception agent, morphine, against the experimental model of tonic continuous pain produced by FORMALIN. FORMALIN (0.1 ml of 1% solution) was injected under the plantar surface of right hind paw of mice and the time an animal spent in liking the injected paw was measured. Gossypin was administered before the induction of pain by FORMALIN and its effect was measured compare with morphine. Gossypin exracted from Hibiscus Vitifolus Linn plant has got naalgesic effect compared to morphine. It is recommended to survey the antiinflammatory effects of gossypin and Hibiscus Vitifolus Linn extract to find the relationship between the good analgesic effect and likely antiinflammatory effect.

Backgrounds: Vanillin is the active component of Vanillus planifolia seeds and is widely used as a flavoring agent in food and pharmaceutical industries. It has shown anti-inflammatory and antinociceptive properties. The aim of the present research was to investigate its possible mechanism(s) in FORMALIN test. Methods: Male Swiss mice (25–30 g) were used. FORMALIN test was used to evaluate the antinociceptive effect. Different groups of mice were pretreated with prazocin (2 mg/kg), yohimbine (5 mg/kg), propranolol (2 mg/kg), cyproheptadine (2 mg/kg), ondansetron (2 mg/kg), naloxone (5 mg/kg), sulpiride (20 mg/kg), arginine (100 mg/kg), L-NAME (20 mg/kg), methylene blue (5 mg/kg), or glibenclamide (10 mg/kg) to evaluate the role of pertinent receptors or pathways on vanillin-induced antinociception. Results: Vanillin showed antinociceptive effect in the second phase of FORMALIN test. Pretreatment with ondansetron, sulpiride, L-NAME, methylene blue, or glibenclamide prevented vanillin antinociceptive effect. Conclusions: Vanillin showed antinociceptive effect in FORMALIN test, and according to the results, the NO/cGMP/KATP pathway and serotonin 5HT3 and dopamine D2 receptors have an important contribution to its antinociceptive effect, but opioid and adrenergic receptors are not involved in this effect.