Involvement of H2-receptors in the mechanism of analgesic action of Tyr-MIF-1.

The antinociceptive effects of H2-agents cimetidine (CIM) and dimaprit (DMP) as well as their effects on the Tyr-MIF-1-evoked analgesia have been studied after intraperitoneal (i.p.) administration in rats. In the paw-pressure (PP) test Tyr-MIF-1 (1 mg/kg), CIM (50 and 100mg/kg) and DMP (5 and 10mg/kg) induced analgesia. Injected before DMP, naloxone (NAL) and CIM diminished or completely prevented the pain-relieving effect of H2-agonist DMP. The antinociceptive effect of Tyr-MIF-1 has been potentiated by DMP dose-dependently. CIM (50mg/kg) decreased the antinociceptive action of the combination Tyr-MIF-1 + DMP, while CIM (100mg/kg) expressed a weaker inhibitory effect on it. The data obtained clearly show that H2-receptor activation is involved in the mechanism of the Tyr-MIF-1 antinociceptive action.