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Background: Oxidative stress is one of the probable molecular mechanisms involved in lead (Pb) neurotoxicity. On the other hand, lemon balm (Melissa officinalis) which is widely used in traditional medicine, has a high antioxidant activity. In this study, the protective impacts of Melissa officinalis on the adverse effects of Pb toxicity on learning ability were investigated. Materials and Methods: In this experimental-clinical trial, 40 virgin Wistar rats were mated and divided into control, control positive (vitamin C+Pb), control negative (Pb), and 3 Pb and Mellisa experimental groups. Mellisa was orally administered in three doses including + 25, 50 and 100 mg/ kg of body weight daily. Treatment started from 7th day of gestation and continued through pregnancy and lactation periods. The three month- old offsprings in each group were assessed in terms of memory and learning ability by Morris water maze test and the results were compared between the groups. Results: Exposure to Pb during and after gestation leads to learning disorders. While concomitant administration of Pb and Melissa, as well as vitamin C can, to a large degree, reduce the adverse effects of Pb on learning abilities. Conclusion: Since no significant differences were obtained from the comparison of results in the control, Pb+M and vitamin C+Pb groups, it can be concluded that Melissa has antioxidant impacts equal to vitamin C. Therefore, similar to vitamin C, Mellisa can decrease the neurotoxic effects of Pb.

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Background: Since the anti-inflammatory effects of usual doses of morphine (10mg/kg) is proved, and also, regarding to the role of C-fibers in the release of substance P and CGRP and progression of inflammation were found, and the other hand, the excitatory effects of very low doses of morphine (1µg/kg) on C-fibers have also been reported, present study has examined the role of C-fibers, usual and very low doses of morphine in presence or reduced C-fibers on paw edema induced by sub plantar injection of formalin.

Materials & Methods: In this study, male Wistar rats (180-200g) were Categorized into two groups. One as vehicle (which received neonatal capsaicin vehicle, C-normal) and experimental (which received neonatal capsaicin, C-lesion). Each category contains three groups which were treated by saline, 10 mg/kg and 1µg/kg of morphine (i.p). In each group, paw edema volume induced by injection of 0.05 cc of 2.5% formalin, was acquired by plethysmometric test.

Results: In C-normal groups, morphine showed an anti-inflammatory effect at the dose of 10mg/kg (p<0.01) and pro-inflammatory effect at the dose of 1µg/kg (p<0.01). Reduction of C-fibers in C-lesion groups diminished the inflammation induced by formalin (p<0.001). Also in these groups, 10 mg/kg dose of morphine showed a more potent anti-inflammatory effects (p<0.001) and the pro-inflammatory effects of 1µg/kg dose of morphine reduced (p<0.001).

Conclusion: C-fibers by releasing substance P and CGRP can play an important role in inflammation induction in injured tissue. The results showed that, the reduction of these fibers can lead to inflammation reduction. So, the presences of C-fibers are so important in inflammation induction and edema.