Substance P-induced cutaneous plasma extravasation in rats is mediated by NK-1 tachykinin receptors

Substance P (SP), a relatively non-selective tachykinin receptor agonist, and Septide and Senktide, highly selective NK-1 and NK-3 tachykinin receptor agonists, respectively, were injected intradermally in rats. The resulting cutaneous plasma extravasation (PE) was evaluated by measuring the amount of Evans blue that leached from the circulation into the skin. SP and Septide produced dose dependent PE. Septide being the more potent of the two. Senktide did not produce PE, even at doses 10,000 times higher. Neonatal capsaicin treatment significantly reduced SP- and Septide-induced PE. These data indicate that SP-induced PE is mediated by NK-1 tachykinin receptors.