Independent endocytosis of the NK1 and NK3 tachykinin receptors in neurons of the rat myenteric plexus

Abstract

In the myenteric plexus of rat ileum, NK(1) and NK(3) receptors are co-located almost exclusively on neurons of a single population. This study compares endocytosis of NK(1) and NK(3) receptors in these neurons. In the absence of agonist, 26.2+/-2.8% of NK(1) receptor and 29.1+/-1.1% of NK(3) receptor was located in the cytoplasm of the neurons; the remaining receptor was on the surface. The tachykinin neurotransmitters, substance P (10 pM-10 microM) and neurokinin A (10 pM-100 microM), both induced concentration-dependent endocytosis of NK(1) and NK(3) receptors. The selective NK(1) receptor agonist, [Sar(9),Met(O(2))(11)]-substance P (1 microM), induced endocytosis of NK(1) receptor (64.2+..