Injected intrathecally, bradykinin (BK) produced either hyperalgesia (0.15 µg) or antinociception (6.0 µg) in rats when thermal noxious stimuli were used. Similarly, des-Arg⁹-BK at the lower dose (0.15 µg) decreased, whereas at the higher dose (6.0 µg) it increased the threshold to thermal noxious stimuli; however, these effects were less pronounced than those of BK. The antinociception induced by BK was abolished by HOE 140, a B₂ receptor antagonist, injected intrathecally at a dose of 1.3 ng and was markedly attenuated by des-Arg¹⁰-HOE 140, a B₁ receptor antagonist (1.15 ng i.t.). The results obtained in this study showed that – depending on the dose used – BK and des-Arg⁹-BK could produce pro- as well as antinociceptive actions. Both B₂ and B₁ receptors are involved in the action of intrathecally applied BK.