[Sar9]-Substance P is one of NK-1 receptor agonist. The action of SP on progesterone metabolism was mimicked by the rNK1-specific agonist [Sar-9,Met(O2)11]-SP.

Sar9, Met (O2)11-Substance P is a neurokinin-1 receptor agonist. It is an analog of the naturally occurring human neuropeptide Substance P, which can be found throughout the body, including in the airways of humans and many other species.

Hemokinin 1 (mouse) is a selective excitogen 1 receptor agonist with a Ki value of 0.175 nM for the human NK1 receptor and 560 nM for the human NK2 receptor.