Evaluation of (D-Pro2, D-Trp7,9)-substance P as an antagonist of substance P responses in the rat central nervous system.

The (D-Pro2, D-Trp7,9) analogue of substance P has been tested for substance P antagonist activity in the caudal trigeminal nucleus in vivo, and in the isolated spinal cord in vitro. In neither case was the analogue found to be a specific antagonist of substance P, although the analogue did have weak antagonist actions in the isolated guinea-pig ileum preparation. It is concluded that the analogue is not a suitable tool for the identification of putative substance P systems in the spinal cord or the caudal trigeminal nucleus of the rat.