Sumatriptan improves the locomotor activity and neuropathic pain by modulating neuroinflammation in rat model of spinal cord injury.

OBJECTIVES: To investigate the therapeutic effects of sumatriptan in a rat model of spinal cord injury (SCI) and possible anti-inflammatory and analgesic mechanisms underlying this effect. METHODS: Using an aneurysm mini-clip model of contusive SCI, T9-10 laminectomies were performed for 60 male rats. Animals were divided into six experimental groups (n = 10 per group) as follows: a minocycline administered positive control group, a saline-vehicle negative control group, a sham-operated group, and three experimental groups which received separate doses of sumatriptan (0.1, 0.3 and 1 mg/kg). Behavioural assessments were used to evaluate locomotor activity and neuropathic pain for 28 days. At the end of the study, spinal cord tissues were collected from sacrificed animals for histopathological analysis. Levels of calcitonin gene-related peptide (CGRP) and two pro-inflammatory cytokines (tumor necrosis factor [TNF]-α and interleukin [IL]-1ß) were assessed by the enzyme-linked immunosorbent assay (ELISA). RESULTS: Sumatriptan significantly (P < 0.001) improved the locomotor activity in SCI group. Sumatriptan was also more effective than the positive control, i.e. minocycline (0.3 mg/kg). Additionally, sumatriptan and minocycline similarly attenuated the mechanical and thermal allodynia in SCI (P < 0.001). TNF-α, IL-1ß and CGRP levels in sumatriptan- and minocycline-treated groups significantly (P < 0.001) decreased compared to controls. Histopathological analysis also revealed a markedly improvement in hemorrhage followed by inflammatory cell invasion, neuronal vacuolation, and cyst formation in both sumatriptan- and minocycline-treated groups compared to control animals. CONCLUSIONS: Sumatriptan improves functional recovery from SCI through its anti-inflammatory effects and reducing pro-inflammatory and pain mediators.

Evaluation of the pharmacological involvement of ATP-sensitive potassium (KATP) channels in the antidepressant-like effects of topiramate on mice.

Acute doses of topiramate (TPM) have been shown to reduce immobility time in the mice forced swimming test (FST) through inhibition of the nitric oxide (NO) pathway. Adenosine triphosphate-sensitive potassium (KATP) channels are known to have an active role in depression. This study investigates the potential participation of KATP channels in the antidepressant-like effect of TPM through the stimulatory effects of NO. FST and tail suspension tests (TST) were applied to adult male mice for assessment of the antidepressant-like activity of TPM. Different doses of glibenclamide and cromakalim were also applied in order to investigate the involvement of KATP channels. Fluoxetine was used as a positive control for evaluation of antidepressant-like effects. In addition, each animal's locomotor activity was evaluated by the open-field test (OFT). TPM (30 mg/kg intraperitoneal (i.p.)) had a significant reductive effect on the immobility behavior similar to fluoxetine (20 mg/kg). Co-administration of sub-effective doses of glibenclamide (1 mg/kg i.p.) and TPM (10 mg/kg i.p.) led to significant synergistic effects in FST and TST. Additionally, the results showed that administration of the sub-effective dose of cromakalim (0.1 and 0.3 mg/kg i.p.) blocked the antidepressant-like effects of TPM (30 mg/kg i.p.) in both tests. These interventions had no impact on the locomotor movement of mice in OFT. This study shows that the antidepressant-like activity of TPM may potentially be mediated by the blocking of the KATP channels.

Acute Activation of α7-Nicotinic Receptors by Nicotine Improves Rodent Skin Flap Survival Through Nitrergic System.

BACKGROUND: Recent reports have identified angiogenic, anti-inflammatory, and antioxidant properties of acute treatment with nicotine via activation of nicotinic acetylcholine receptors (nAChRs). In addition, the nitric oxide (NO) pathway is involved in ischemic reperfusion injuries. OBJECTIVES: We investigated the effects of acute pretreatment with nicotine in a rat model of random-pattern skin flap and the potential role of the NO pathway. METHODS: The Sprague-Dawley rats received increasing doses of (-)-nicotine (0.5, 1, 1.5, 2, and 3 mg/kg) before the procedure. Dorsal skin flaps with caudal pedicles were elevated at the midline, and flap survival was evaluated 7 days after surgery. In addition, animals received an α7-nAChR antagonist, methyllycaconitine, with nicotine. Quantitative reverse transcription polymerase chain reaction was also applied to measure the dermal expression of α7-nAChR. Next, a nonselective NO synthase inhibitor, N-nitro-L-arginine methyl ester hydrochloride; a selective inducible NO synthase inhibitor, aminoguanidine; and an NO precursor, L-arginine, were administered with nicotine. RESULTS: Nicotine at doses of 1, 1.5, and 2 mg/kg significantly increased flap survival, whereas the protective effects of nicotine disappeared at higher doses. Methyllycaconitine completely reversed the protective effects of nicotine and the elevated cutaneous expression of α7-nAChR in nicotine-pretreated rats. In addition, systemic administration of N-nitro-L-arginine methyl ester hydrochloride or aminoguanidine with an effective dose of nicotine caused a significant decrease in flap survival. Conversely, coinjection of a subeffective dose of L-arginine with the subeffective dose of nicotine significantly boosted its protective effects. CONCLUSIONS: Acute pretreatment with nicotine by stimulating the expression and activation of cutaneous α7-nAChR improves skin flap survival, which is partially mediated through modulation of the NO pathway.