Iranian

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Background: Hippocampal damages, which are accompanied by inflammation, are among the main causes of epilepsy acquisition. We previously reported that chronic intracerebroventricular (i.c.v.) injection of lipopolysaccharide (LPS) modulates epileptogenesis in rats. There is a network of gap junction channels in the hippocampus that contribute to epileptogenesis. Gap junction channels are formed by oligomeric protein subunits called connexins (Cx). Astrocytic Cx43 and neuronal Cx36 are expressed in the hippocampus. In order to find out the possible role of gap junctions in seizure-modulating effect of LPS and neuroinflammation, we studied the effect of central administration of LPS on expression of Cx36 and Cx43 in rat hippocampus. Methods: LPS, 2.5 µg/rat/day, was injected i.c.v. to male Wistar rats for 14 days. mRNA and protein abundance of Cx36, Cx43 and IL1-β were measured in rat hippocampus by real time-PCR, Western blot and ELISA techniques, at the beginning, in the middle, and at the end of the treatment period. Results: IL1-β protein level was significantly increased 6 h after first injection of LPS. Cx36 and Cx43 mRNA expression did not alter during chronic administration of LPS. A selective decrease in Cx43 protein expression was observed after 7 injections of LPS. Conclusion: It is suggested that Cx43 containing gap junctions in the hippocampus is down-regulated in response to chronic injection of LPS. This event can inhibit propagation of toxic and noxious molecules to neighboring cells and modulate hippocampal excitability and epileptogenesis.

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Background: GABAergic interneurons in the hippocampal CA1 area are mutually communicated by gap junctions (GJs) composed of connexin36 (Cx36). We examined the role of Cx36 in CA1 in manifestation of kindled seizures and hippocampal kindling in rats. Methods: Quinine, as the specific blocker of Cx36, was injected into CA1, and kindled seizures severity was examined 10 min afterward. Moreover, quinine was injected into CA1 once daily, and the rate of CA1 kindling was recorded. Results: Quinine 0.5 and 1 mM caused 2- and 3.5-fold increase in
the duration of total seizure behavior and generalized the seizures. Primary and secondary afterdischarges (AD) were also significantly increased. Quinine 0.1 mM augmented the rate of kindling and the growth of secondary AD. Conclusion: Cx36 GJs in CA1 are the main components of hippocampal inhibitory circuit. Any interruption
in this path by pathologic or physical damages can trigger hippocampal hyperexcitability and facilitate epileptogenesis. to determine its active components precisely where four dominant fractions obtained at retention time of 156-160 minutes. The phospholipase A2 and hemolytic activities of the purified fractions were first evaluated. Then the anti-viral activity was measured using single cycle HIV (NL4-3) replication and HSV (KOS) plaque reduction assays. Results: The H. lepturus crude venom inhibited HIV replication by 73% at the concentration of 200 µg/ml, while it did not show significant anti-HSV activity. It also inhibited the cell-free viral particles in a virucidal assay, while it showed no toxicity for the target cells in a proliferation assay. The four HPLC fractions purified from H. lepturus inhibited HIV with IC₅₀ of 20 µg/ml. Conclusion: H. lepturus venom contains components with considerable anti-HIV activity insofar as it has virucidal activity that offers a novel therapeutic approach against HIV infection. Our results suggest a promising pilot for anti-HIV drug discovery with H. lepturus scorpion venom.

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Background: Gap junctions (GJs) provide direct intercellular communications that are formed by hexameric protein subunits, called connexin (Cx). The role of Cxs in epileptogenesis has not received sufficient attention. Hippocampus with critical function in epileptogenesis has a wide network of GJs. We examined the protein expression levels of hippocampal Cx36 (the prominent Cx present between GABAergic interneurons) and Cx43 (the main Cx expressed by astrocytes) during epileptogenesis in the pilocarpine model of epilepsy. Methods: Male Wistar rats received scopolamine (1 mg/kg, s.c.). Pilocarpine (380 mg/kg, i.p.) was administered 30 min thereafter to induce status epilepticus (SE). SE was stopped 2 h later by diazepam (10 mg/kg, i.p.). Cx36 and Cx43 protein expression was assessed by Western blot analysis in the hippocampus of SE-experienced rats, after injection of diazepam (F0 subgroup), after acquisition of focal seizures (F3 subgroup), and after development of generalized seizures (F5 subgroup). The control subgroups, C0, C3, and C5, were aged-matched rats, which received saline (1 ml/kg, i.p.) instead of pilocarpine. Injection of scopolamine and diazepam, and dissection of hippocampi were carried out at the same time interval as the test subgroups. Results: SE emerged in 67.1% of pilocarpine-treated animals. Focal and generalized seizures developed 3.8±0.4 and 7.0±0.5 days after SE, respectively. Cx36 protein abundance was not significantly different between test and control groups in the three time points. However, Cx43 protein level showed 40% increase in F3 subgroup (P<0.05 compared to C3, P<0.01 compared to F0 and F5). Conclusion: Hippocampal Cx43 is overexpressed in pilocarpine model of epileptogenesis after acquisition of focal seizures.