Contribution of dopaminergic and adenosinergic systems in the antinociceptive effect of p-chloro-selenosteroid.

This study investigated the antinociceptive action of p-chloro-selenosteroid (PCS), administered by intragastric route (i.g.) to mice against acute models. The contribution of adenosinergic, dopaminergic, serotonergic, nitric oxide and opioid systems was investigated. It was evaluated if the administration of PCS triggers toxic effect. Treatment with PCS (10mg/kg) reduced writhing induced by acetic acid and its effect lasts up to 48 h after treatment. The compound caused an inhibition in neurogenic and inflammatory phases of nociception and in paw edema induced by formalin. The licking behavior triggered by glutamate was reduced by PCS. In the tail-immersion test, PCS elicited an increase in delta latency response. Pretreatment with caffeine (3mg/kg, intraperitoneally [i.p.]) and SCH58261 (3mg/kg, i.p.), antagonist at adenosinergic receptors, SCH23390 (0.05 mg/kg, i.p.) and sulpiride (5mg/kg, i.p.), antagonist at dopaminergic receptors, caused a reduction in the antinociceptive action of PCS in the glutamate test. By contrast, pretreatment with WAY100635 (0.7 mg/kg, i.p.), ketanserin (0.3mg/kg, i.p.), ondasentron (0.5mg/kg, i.p.), l-arginine (600 mg/kg, i.p.) and naloxone (1mg/kg, subcutaneous [s.c.]) did not abolish the antinociceptive effect caused by PCS (10mg/kg, i.g.) administration. The animals treated with PCS did not show alterations in locomotor and exploratory activities, in biochemical parameters evaluated, food and water consumption, as well as in the body weight. These results clearly showed the antinociceptive action of PCS in different animal models without causing acute toxic effects in mice. Adenosinergic and dopaminergic systems seem to be related to the mechanisms by which PCS elicits antinociception.