ABSTRACT
Pain is a major cause of distress, both physical and psychological. There is a continuous search for new pharmacologically active analgesic agents with minor adverse effects. Recently, the synthesis of (-)-(2S,6S)-(6-ethyl-tetrahydropyran-2-yl)-formic acid [tetrahydropyran derivative (TD)] was described. The objective of this study was to investigate antinociceptive effects of TD. Its activity was compared with the activity of morphine. The effects of TD and morphine were evaluated in models of inflammatory and noninflammatory pain. TD (6-1200 µmol/kg, intraperitoneally) significantly reduced the nociceptive effects induced by acetic acid or formalin in mice. TD also demonstrated an antinociceptive effect in the tail-flick and hot-plate model. The opioid receptor antagonist, naloxone (at 15 µmol/kg, intraperitoneally), reversed the antinociceptive activity of TD in all the models evaluated. Morphine and TD induced tolerance in mice. However, the onset of tolerance to TD was delayed compared with that induced by morphine. These results indicate that TD develops significant antinociceptive activity and, at least part of its effects seems to be mediated by the opioid system.
Subject(s)
Analgesics, Opioid/pharmacology , Analgesics/pharmacology , Formates/pharmacology , Morphine/pharmacology , Pyrans/pharmacology , Acute Pain/drug therapy , Analgesics/administration & dosage , Analgesics, Opioid/administration & dosage , Animals , Disease Models, Animal , Dose-Response Relationship, Drug , Drug Tolerance , Formates/administration & dosage , Male , Mice , Morphine/administration & dosage , Naloxone/pharmacology , Narcotic Antagonists/pharmacology , Pyrans/administration & dosageABSTRACT
Brillantaisia palisotii Lindau is a plant belonging to Acanthaceae family and it is widely found in tropical regions. Some species of this family are used in the folk medicine to treat several disorders, mainly those that involve analgesic processes. In this work it was evaluated antinociceptive activities of dichloromethane, ethyl acetate and n-butanol extracts obtained from Brillantaisia palisotii stems in peripheral (acetic acid-induced writhing) and central (tail flick and hot plate) analgesic models. All three extracts significantly inhibited the total number of writhing in a dose dependent manner. A spinal antinociceptive effect was observed with all three extracts and with similar patterns to all doses (1-30 mg/kg). Although ethyl acetate extract did not demonstrate supra-spinal activity, the effects observed with dichloromethane extract showed analgesic effect with all doses. The n-butanolic extract had activity only with the lowest dose (1 mg/kg). Our results indicate that all extracts from Brillantaisia palisotti stems develop peripheral and spinal analgesic activity, being the dichloromethane extract the only one with supra-spinal analgesic effect.
