Figure 9. ECE-1-mediated recycling of the NK₁R in response to endogenous SP in myenteric neurones.

Organotypic preparations of mouse colon were unstimulated or stimulated with KCl (50 mm, 5 min), washed and recovered for 30 or 60 min. NK₁R was localized in whole-mounts of myenteric plexus by immunofluorescence (A) and pixel intensity at the plasma membrane (PM) and within the cytosol (CYT) was determined (B). In unstimulated neurones, NK₁R-IR remained at the plasma membrane (arrowheads). KCl stimulated trafficking to endosomes at 30 min (arrows), and recycling to the plasma membrane at 60 min (arrowheads). The ECE-1 inhibitor SM-19712 did not affect endocytosis at 30 min, but caused NK₁R retention in endosomes (arrows), and thus suppressed recycling at 60 min. The NK₁R antagonist RP-67580 prevented KCl-induced endocytosis at 30 min. Scale, 10 μm. *P < 0.05 compared to no KCl at 30 min; ^†P < 0.05 compared to KCl at 60 min. 12–39 neurones per group from n = 3 mice.