Using immunohistochemical analysis, we investigated the time profile of neuronal nitric oxide synthase (nNOS) expression in the lumbar spinal cord up to day 28 after transection of the L 5 spinal root. On day 14 after injury, we also evaluated the effect of intrathecal application of 7-nitroindazole (7-NI), a selective nNOS inhibitor (8.15 µg in 5 µl), on thermal hyperalgesia. Our results indicated that nerve transection increased the intensity of nNOSimmunoreactivity in superficial and deep laminae of the dorsal horn within a late stage (days 7 to 28) of the neuropathy model used. Furthermore, 7-NI attenuated nerve injury-evoked thermal hypersensitivity on day 14 but did not reduce it between days 2 and 5 after transection. These data suggest that nNOS overexpression is more involved in the development than in the initiation of thermal hyperalgesia in L 5-transected rats.

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IntroductionHypothyroidism is one of the most prevalent exocrine gland disorders. It occurs in females 8-10 times more than males.1,2 Its prevalence depends directly on age. Hypothyroidism is caused by inadequate production and storage of thyroid hormones.3 Thyroid hormone is essential for the normal functioning of some tissues in the body. 4 Patients with hypothyroidism usually complain a lot about delay in the wound healing, dermatophytosis and post-surgical pains. In the past decades, different methods have been proposed to accelerate wound healing and decrease the side effects of healing. Modalities such as laser have been proposed alongside pharmacotherapy. 5Mester et al discovered the advantages of laser to wound healing. 6 All studies on lab animals emphasize that lowlevel laser accelerates wound healing through increased proliferation of fibroblasts and formation of fibrous granulation, increased collagen synthesis and ATP production, lymphocytes activation as well as increased ability to attach to pathogens. 7 In laser therapy, various parameters are important including wavelength, frequency, and duration of the radiation.8 Numerous lasers are being used to heal wounds, including the gallium-aluminum arsenide laser. Hypothyroidism is associated with delayed wound healing. Laser therapy may stimulate wound regeneration. The aim of this study was to determine the combined effects of levothyroxine and low level laser therapy during the wound healing process on skin of hypothyroidism male rat model. Methods: Thirty male Wistar rats were randomly divided into 5 groups: control group, hypothyroidism group, hypothyroidism group treated by laser, hypothyroidism group treated by levothyroxine, and hypothyroidism group treated by laser and levothyroxine. To induce hypothyroidism, methimazole was given at a dose of 4 mg/100 mL in their drinking water. After hypothyroidism was proven through immunoassay commercial kit, rats were generally anesthetized with ketamine and xylazine, then, an incisional skin wound was created in a length of 1.2 cm on the back of the ribcage. The surgical day is considered as the zero day. The third and fifth groups were treated with a pulse laser, 810 nm wavelength 80 Hz frequency and 0.2 J/cm 2 energy densities for 200 seconds. Levothyroxine was injected to the fourth and fifth groups intraperitoneally. On the 14th day, a normal sample of each healing skin wound was harvested for biomechanical examination. The obtained data were analyzed by the SPSS software 21 and reported as a mean ± standard error of mean (SEM). P < 0.05 was considered statistically significant. Results:The results showed that the mean maximum force and the accomplished work (energy) made a significant difference in the group receiving both laser and levothyroxine synchronously rather than the other groups (P ≤ 0.05). The elasticity of the wound healing in the groups that received laser and levothyroxine synchronously was significantly higher in comparison with the control and hypothyroidism groups but the differenc...

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Please cite this article as follows: Firouzi A, Norozian M, Amini A, Abdollahifar MA, Abbaszadeh HA, Fadaei Fathabadi F. Combined effect of low-level laser treatment and levothyroxine on wound healing in rats with hypothyroidism. AbstractIntroduction: Hypothyroidism delays wound healing by reducing the synthesis of keratinocytes, fibroblast cells, and collagen. Methods for enhancement of wound healing include laser therapy and hormone therapy. The current study evaluated the combined effect of laser and levothyroxine therapy to cure wounds in male rats with hypothyroidism. Methods: Sixty male Wistar rats were randomly divided into 5 groups: (1) healthy controls;(2) controls with hypothyroidism; (3) hypothyroidism + laser treatment; (4) hypothyroidism + levothyroxine treatment; (5) hypothyroidism + laser + levothyroxine treatment. Hypothyroidism was induced by dissolving 4 mg of methimazole in 100 mL of drinking water daily for 28 days. After hypothyroidism had been confirmed, a longitudinal incisional wound was created on the dorsal rib cages of the rats. The wounds that received laser treatment were divided into 12 sections and treated at 810 nm wavelength and 0.2 J/cm 2 of energy density for 200 seconds. Levothyroxine was administrated in doses of 20 µg/kg/d i.p. All groups were divided into 3 subgroups for testing on days 4, 7 and 14. Samples were collected in all the subgroups. Results: The results showed that hypothyroidism reduced fibrous tissue volume, fibroblasts, and basal cell numbers. The combined effect of laser and levothyroxine improved all parameters. Conclusion: Combined laser and levothyroxine treatment showed the best effect on wound healing and accelerated the closure of the wounds.