Antihyperalgesic effects of vanilloid-1 and bradykinin-1 receptor antagonists following spinal cord injury in rats.

Object: The authors previously discovered that genes for the bradykinin-1 (B1) receptor and the transient receptor potential vanilloid subtype 1 (TRPV1) were overexpressed in animals exhibiting thermal hyperalgesia (TH) following spinal cord injury (SCI). They now report the effect of TRPV1 (AMG9810) and B1 (Lys-[Des-Arg9,Leu8]-bradykinin) antagonists on TH in animals following SCI.

Methods: The rats were subjected to contusion SCI and then divided into groups in which TH did or did not develop. The animals from both groups were given either AMG9810, Lys-(Des-Arg9,Leu8)-bradykinin, or the drug-specific vehicle (control groups). Animals were tested for TH preinjury and at regular intervals after SCI by using the hindlimb withdrawal latency test.

Conclusions: The administration of AMG9810 likely improves TH as a result of a generalized analgesic effect, whereas the effect of Lys-(Des-Arg9,Leu8)-bradykinin appears more specific to the reversal of TH. This information has potential usefulness in the development of treatment strategies for post-SCI neuropathic pain.