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

Abstract

In the myenteric plexus of rat ileum, NK1 and NK3 receptors are co-located almost exclusively on neurons of a single population. This study compares endocytosis of NK1 and NK3 receptors in these neurons. In the absence of agonist, 26.2±2.8% of NK1 receptor and 29.1±1.1% of NK3 receptor was located in the cytoplasm of the neurons; the remaining receptor was on the surface. The tachykinin neurotransmitters, substance P (10pM-10μM) and neurokinin A (10pM-100μM), both induced concentration-dependent endocytosis of NK1 and NK3 receptors. The selective NK1 receptor agonist, [Sar9, Met(O2)11]-substance P (1μM), induced endocytosis of NK1 receptor (64.2±1.5% in cytoplasm) but not NK3 receptor (32.9±..