EXOGENOUS GASEOUS SUPEROXIDE POTENTIATES THE ANTINOCICEPTIVE EFFECT OF OPIOID ANALGESIC AGENTS

The study examined the potentiation of the antinociceptive action of o pioid analgesics produced by gaseous superoxide (GS) in the rat hind p aw withdrawal test (PWT) and by GS or hydrogen peroxide (HP) in the fo rmalin test. In the PWT, inhalation of GS for 50 minutes before i.p. i njection of threshold doses of morphine (0.5 mg/kg) and trimeperidine (1.0 mg/kg) increased the threshold of nociception (TN) by a maximum o f 43.0% (p<0.05) and 113.4% (p<0.01) respectively. The GS/trimeperidin e-dependent increase in TN showed two peaks, the second of which could be suppressed by nialamide. Naloxone abolished the GS/morphine-depend ent increased in the TN. In the formalin test, a significant antinocic eptive effect developed after GS inhalation or HP administration (intr anasally, 2 x 5 mu l of 2 x 10(-5) mol/l solution in saline) in combin ation with low doses of Omnopon (0.06-0.75 mg/kg). These results sugge st that both GS and HP potentiate the antinociceptive effects of opioi d analgesics.