The effect of Ocimum basilicum total extract on the development of tolerance to morphine analgesia in male rats

Abstract

<strong>Background and objectives:</strong> Long-term exposure to opiates induces tolerance to the analgesic effect. The chronic use of opioids in glia cells produces pro-inflammatory mediators such as Tissue Necrosis Factor α and interleukins. Regarding the reports on <em>Ocimum basilicum </em>(Family: Lamiaceae) which has antioxidant and anti-inflammatory effects, it is probable that it could delay the tolerance to analgesic effect of morphine. <strong>Methods:</strong> Ethanol extract of <em>O. basilicum</em> was obtained via maceration method. Existence of rosmarinic and caffeic acids as the dominant components of the extract was revealed according to the thin-layer chromatography approach in the presence of standard compounds. Groups of rats received daily morphine (10 mg/kg, intraperitoneal; <em>i</em><em>.</em><em>p</em><em>.</em>) in combination with vehicle or the ethanol extract (20, 40, 80 mg/kg, <em>i</em><em>.</em><em>p</em><em>.</em>). The last group of rats received ethanol extract alone (40 mg/kg, <em>i</em><em>.</em><em>p</em><em>.</em>) which was the lowest effective dose of the extract. Nociception was assessed using hotplate apparatus (55 °C). <strong>Results: </strong><em>Ocimum basilicum</em> contained valuable antioxidant compounds such as rosmarinic and caffeic acids. Morphine tolerance was completed after the 7^th day in the control and vehicle groups. Morphine tolerance was completed in the 9^th day (<em>p</em><0.05) with 20 mg/kg of the extract. On the other hand, tolerance was completed with 40 mg/kg and 80 mg/kg of the extract in the 13^th day and 15^th day respectively (<em>p</em><0.001) and the lowest effective dose of extract (40 mg/kg, <em>i</em><em>.</em><em>p</em><em>.</em>) without morphine had no analgesic effect. <strong>Conclusion</strong>:Theresults showed that the ethanol extract of <em>O. basilicum</em> dose dependently delayed morphine induced tolerance.

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