Neuroprotective effect of minocycline on cognitive impairments induced by transient cerebral ischemia/reperfusion through its anti-inflammatory and anti-oxidant properties in male rat.

Memory deficit is the most visible symptom of cerebral ischemia that is associated with loss of pyramidal cells in CA1 region of the hippocampus. Oxidative stress and inflammation may be involved in the pathogenesis of ischemia/reperfusion (I/R) damage. Minocycline, a semi-synthetic tetracycline derived antibiotic, has anti-inflammatory and antioxidant properties. We evaluated the neuroprotective effect of minocycline on memory deficit induced by cerebral I/R in rat. I/R was induced by occlusion of common carotid arteries for 20min. Minocycline (40mg/kg, i.p.) was administered once daily for 7days after I/R. Learning and memory were assessed using the Morris water maze test. Nissl staining was used to evaluate the viability of CA1 pyramidal cells. The effects of minocycline on the microglial activation was also investigated by Iba1 (Ionized calcium binding adapter molecule 1) immunostaining. The content of malondialdehyde (MDA) and pro-inflammatory cytokines (IL-1ß and TNF-α) in the hippocampus were measured by thiobarbituric acid reaction substances method and ELISA, respectively. Minocycline reduced the increase in escape latency time and in swimming path length induced by cerebral I/R. Furthermore, the ischemia-induced reduction in time spent in the target quadrant during the probe trial was increased by treatment with minocycline. Histopathological results indicated that minocycline prevented pyramidal cells death and microglial activation induced by I/R. Minocycline also reduced the levels of MDA and pro-inflammatory cytokines in the hippocampus in rats subjected to I/R. Minocycline has neuroprotective effects on memory deficit induced by cerebral I/R in rat, probably via its anti-inflammatory and antioxidant properties.

Protective effect of α-terpineol against impairment of hippocampal synaptic plasticity and spatial memory following transient cerebral ischemia in rats.

OBJECTIVES: Cerebral ischemia is often associated with cognitive impairment. Oxidative stress has a crucial role in the memory deficit following ischemia/reperfusion injury. α-Terpineol is a monoterpenoid with anti-inflammatory and antioxidant effects. This study was carried out to investigate the effect of α-terpineol against memory impairment following cerebral ischemia in rats. MATERIALS AND METHODS: Cerebral ischemia was induced by transient bilateral common carotid artery occlusion in male Wistar rats. The rats were allocated to sham, ischemia, and α-terpineol-treated groups. α-Terpineol was given at doses of 50, 100, and 200 mg/kg, IP once daily for 7 days post ischemia. Morris water maze (MWM) test was used to assess spatial memory and in vivo extracellular recording of long-term potentiation (LTP) in the hippocampal dentate gyrus was carried out to evaluate synaptic plasticity. Malondialdehyde (MDA) was measured to assess the extent of lipid peroxidation in the hippocampus. RESULTS: In MWM test, α-terpineol (100 mg/kg, IP) significantly decreased the escape latency during training trials (P<0.01). In addition, α-terpineol increased the number of crossings over the platform location and decreased average proximity to the target in probe trial (P<0.05). In electrophysiological recording, α-terpineol (100 mg/kg) facilitated the induction of LTP in the hippocampus which was persistent over 2 hr. α-Terpineol (100 and 200 mg/kg) also significantly lowered hippocampal MDA levels in rats subjected to cerebral ischemia. CONCLUSION: These findings indicate that α-terpineol improves cerebral ischemia-related memory impairment in rats through the facilitation of LTP and suppression of lipid peroxidation in the hippocampus.

The attenuation of pain behaviour and serum interleukin-6 concentration by nimesulide in a rat model of neuropathic pain.

Background Evidence for a role of immune system in hyperalgesic pain states is increasing. Recent work in neuroimmunology suggests that the immune system does more than simply perform its well known functions of recognizing and removing invading pathogens and tumors. Interest in neuroinflammation and neuroimmune activation has grown rapidly in recent years with the recognition of the role of central nervous system inflammatiom and immune responses in the aetiology of pain states. Among various theories, the role of inflammatory responses of the injured nerve has recently received attention. Cytokines are heterogenous group of polypeptides that activate the immune system and mediate inflammatory responses, acting on a variety of tissue, including the peripheral and central nervous system. Interleukin-6 (IL-6) a pro-inflammatory cytokine, is potentially important in pain aetiology, have pronociceptive actions. Neuropathic pain may be due to a primary insult to the peripheral or central nervous system. Substances released during inflammation from immune cells play an important role in the development and maintenance of chronic pain. Nimesulide, a highly selective cox-2 inhibitor, effectively reduces hyperalgesia due to peripherally administration of inflammatory agents like formalin. The safety of nimesulide was reported for some conditions in which other NSAIDs are contraindicated. Here we have determined the effect of nimesulide on pain behaviour and serum IL-6 level in chronic constriction injury (CCI) model of neuropathic pain. Methods Experiments were carried out on male Wistar rats, (weight 150-200 g, n = 8). Rats were divided into 3 different groups: 1-CCI + saline 0.9% 2Sham + saline 0.9% (control) 3CCI + drug. Nimesulide (1.25, 2.5, 5 mg/kg, i.p.) was injected 1h before surgery and continued daily to day 14 post-ligation. 42 °C water for thermal hyperalgesia, von Frey filaments for mechanical allodynia, acetone test for cool allodynia and 10 °C water for cold hyperalgesia were respectively used as pain behavioural tests. Behavioural tests were recorded before surgery and on postoperative days 1, 3, 5, 7, 10, 14 and the serum concentration of IL-6 was determined at the day 14. Results The results of this study showed a decrease in hyperalgesia and allodynia following nimesulide administration. Conclusions It appears that nimesulide was able to reduce pain behaviour due to nerve inflammation and a parallel decrease in the serum IL-6 concentration was observed. Implications The immune system is an important mediator in the cascade of events that ultimately results in hyperalgesia. Cytokines contribute to the patheogenesis of neuropathic pain, therefore drugs that inhibit cytokine release from immune cells may reduce inflammatory pain states.

Suppression of interleukin-6 by minocycline in a rat model of neuropathic pain.

Inflammatory mediators produced in the injured nerve have been proposed as contributing factors in the development of neuropathic pain. In this regard an important role is assigned to interleukin-6. The present study, evaluated the effect of pretreatment with minocycline, on pain behavior (hyperalgesia and allodynia) and serum level of interleukin-6 in chronic constriction injury (CCI) model of neuropathic pain in rat. Minocycline (5, 10, 20 and 40 mg/kg, i.p.) was injected 1 h before surgery and continued daily to day 14 post-ligation. Behavioral tests were recorded before surgery and on postoperative days 1, 3, 5, 7, 9, 10, 14, and the serum concentration of interleukin-6 was determined at day 14. We observed that minocycline which was reported to have a neuroprotective effect in some neurodegenerative diseases, reversed hyperalgesia and allodynia due to sciatic nerve ligation and inhibited the interleukin-6 production. It seems that minocycline could have an anti-inflammatory and analgesic effect in some chronic pain states.