Study of antinociceptive activity of SSRI (fluoxetine and escitalopram) and atypical antidepressants (venlafaxine and mirtazepine) and their interaction with morphine and naloxone in mice.

OBJECTIVE: to study the probable site of antinociceptive action of SSRI (fluoxetine, escitalopram) and atypical antidepressants (mirtazapine, venlafaxine) and their interaction with morphine and naloxone. MATERIALS AND METHODS: the study was conducted on albino mice (25-35 grams) of either sex. Different doses of morphine (0.5 and 1 mg/kg), fluoxetine (2, 5 and 10 mg/kg), venlafaxine (30, 40 and 50 mg/kg), mirtazapine (3, 5 and 7 mg/kg) and escitalopram (2.5, 5 and 10 mg/kg) were administered subcutaneously to obtain their subanalgesic doses using tail flick analgesiometer. Tail flick latencies were obtained at 15, 30, 60 and 120 min. after drug administration. Naloxone (1 mg/kg) was administered 10 minutes prior to test drug for testing antagonism. OBSERVATIONS: fluoxetine (5 and 10 mg/kg), mirtazapine (5 and 7 mg/kg) and venlafaxine (40 and 50 mg/kg) were found to have antinociceptive activity but not at lower doses. Escitalopram failed to show any antinociceptive activity at any of the doses used. The antinociceptive effect of all the drugs was antagonized by naloxone (1 mg/kg). Further, subanalgesic doses of fluoxetine, mirtazapine and venlafaxine showed analgesic activity with suboptimal dose of morphine (0.5 mg/kg). RESULT AND CONCLUSION: fluoxetine, mirtazapine and venlafaxine have antinociceptive activity whereas escitalopram doesn't; their site of action seems to be the same as that of opioid analgesics ('mue' receptors). However, other pathways (cholinergic, histaminic, noradrenergic, GABAergic) may be involved in mediation of their analgesic activity, deserving further elucidation. Results apparently show that these drugs may be useful in the management of pain as monotherapy or in combination with other opioids.

Evaluation of antipyretic activity of Calotropis gigantea (Asclepiadaceae) in experimental animals.

The roots of Calotropis gigantea have been used in leprosy, eczema, syphilis, elephantiasis, ulceration and cough in the Indian system of traditional medicine. The present communication evaluated its antipyretic activity by using yeast-induced and TAB (Typhoid) vaccine-induced pyrexia in rats and rabbits. In both yeast-induced and TAB vaccine-induced fever, the fever was significantly reduced and the body temperature was normalized by administration of 200 and 400 mg/kg dose intraperitoneally. Based on the results of the present study it can be concluded that the extract of C. gigantea has potential antipyretic activity against both yeast-induced and TAB vaccine-induced fever, indicating the possibility of developing C. gigantea as a cheaper and potent antipyretic agent.

Studies on anti-diarrhoeal activity of Calotropis gigantea R.Br. in experimental animals.

PURPOSE: Calotropis gigantea R. Br. (Asclepiadaceae) a wildly growing plant has been reported to possess number of medicinal properties and other purposes. The purpose of the present study was to evaluate scientifically the anti-diarrheal effects of C. gigantea used traditionally in Indian system of medicine using castor oil-induced diarrhoea model. METHODS: The anti-diarrheal effect of hydroalcoholic (50:50) extract of aerial part of Calotropis gigantea was studied against castor oil-induced-diarrhea model in rats. The gastrointestinal transit rate was expressed as the percentage of the longest distance traversed by the charcoal divided by the total length of the small intestine. The weight and volume of intestinal content induced by castor oil were studied by enteropooling method. RESULTS: Like atropine (3 mg/kg, i.p.) there were significant reductions in fecal out put and frequency of droppings when the plant extracts of 200 and 400 mg/kg doses were administered intraperitoneally compared with castor oil treated rats. All doses of the plant extracts also significantly retarded the castor-oil induced enteropooling and intestinal transit. The dose 100 (P<0.01), 200 and 400 mg/kg significantly inhibited (P<0.001) weight and volume of intestinal content. CONCLUSIONS: The remarkable anti-diarrheal effect of C.gigantea extract against castor oil-induced diarrhea model attests to its utility in a wide range of diarrheal states