Evaluation of anti-nociceptive effect of venlafaxine in experimental animal model of mice

Background: Pain is an unpleasant sensation with varying subjective experience. Its management is always challenging for physicians particularly in case of chronic pain. Chronic pain and depression usually co-exist due to poor quality of life and increase in health care costs posing an individual to suffer from depression. Anti-depressants for pain management are being used successfully using since years. In this study venlafaxine, a newer anti-depressant drug was evaluated for anti-nociceptive activity, tail immersion test an analgesic animal model of albino mice.Methods: Randomly selected albino mice of either sex with reaction time of <6 seconds were included in the study and divided into 7 groups with 6 mice in each group. Grouping was done based on the drug received i.e., venlafaxine 15, 30 and 60 mg/kg, tramadol 10 and 20 mg/kg, control group (normal saline) and combination group venlafaxine 15 mg/kg+tramadol 10 mg/kg. Drugs were administered by intra-peritoneal route.Results: Venlafaxine (30 and 60 mg/kg), tramadol (20 mg/kg) and combination group venlafaxine (15 mg/kg+tramadol 10 mg/kg) has shown significant (p<0.001) increase in tail withdrawal latency compared to control group (normal saline) by tail immersion test. Venlafaxine potentiated anti-nociceptive activity of tramadol on concomitant administration with tramadol. Venlafaxine at 60 mg/kg has comparable anti-nociceptive effect to tramadol at 20 mg/kg.Conclusions: Venlafaxine at doses of 30 and 60 mg/kg is having anti-nociceptive effect, but less potent than tramadol.

Examination of CNS Activity of Rhizomes of Alpinia Oxyphylla.

The study is based on the examination of the CNS activity observed from the methanolic extract of the rhizomes of Alpinia oxyphylla. Tail immersion method in mice has been used for the evaluation of the central pharmacological actions. Similarly acetic-acid induced writhing-test was used for the evaluation of the peripheral pharmacological properties. A significant rise in pain threshold is seen in a dose dependent manner with the methanolic extract of A. oxyphylla at doses of 100, 200 and 400 mg/kg body weight with the tail immersion methods. The methanolic extract at 400 mg/kg dose possessed 73.12% writhing inhibition, (p <0.001) in acetic-acid induced writhing-test that could be compared to the standard, Diclofenac-Na (25 mg/kg) with 75.78% inhibition. Open-field and hole-cross tests have been conducted in mice for further investigation of the extract in support of its neuro-pharmacological actions, where dosedependent suppression of exploratory and motor activities were observed in the tested models. Hence, the above results evidence the presence of CNS depressant and analgesic properties of the plant, A. oxyphylla.

Investigation of Neuropharmacological Activity of Seeds of Alpinia Zerumbet.

The study is based on the investigation of the neuropharmacological and analgesic properties observed from the methanolic extract of the seeds of Alpinia zerumbet. Tail immersion method in mice has been used for the evaluation of the central pharmacological actions. Similarly acetic-acid induced writhing-test was used for the evaluation of the peripheral pharmacological properties. A significant rise in pain threshold is seen in a dose dependent manner with the methanolic extract of A. zerumbet at doses of 100, 200 and 400 mg/kg body weight with the tail immersion methods. The methanolic extract at 400 mg/kg dose possessed 73.12% writhing inhibition, (p <0.001) in acetic-acid induced writhing-test that could be compared to the standard, Diclofenac-Na (25 mg/kg) with 75.78% inhibition. Open-field and hole-cross tests have been conducted in mice for further investigation of the extract in support of its neuropharmacological actions, where dose-dependent suppression of exploratory and motor activities were observed in the tested models. Hence, the above results evidence the presence of CNS depressant and analgesic properties of the plant, A. zerumbet.

Chronic central and peripheral analgesic activity of ethanolic extract of the leaves of clerodendrum viscosum in rodent models.

The aim of the study was to investigate the chronic peripheral analgesic activity of Ethanolic Extract of the leaves of Clerodendrum viscosum (EECV) by acetic acid induced writhing reflex test in mice and chronic central analgesic activity of EECV by tail immersion method in rats. Dried powdered leaves of Clerodendrum viscosum were subjected to solvent extraction by using 90 % ethanol. Based on acute oral toxicity study according to Organization for Economic Cooperation and Development (OECD) guidelines No. 423, three doses of the test drug was selected and were subjected to chronic analgesic activity. EECV showed significant chronic peripheral analgesic activity (p<0.01) in mice in the dose of 200 mg / kg and moderate analgesic activity at the dose of 400 mg/kg (p<0.05) as compared to control and the standard drug Indomethacin. But failed to show any chronic central analgesic activity by tail immersion method at any of the three doses selected compared to control and standard drug Pentazocin in rats.