Immunohistochemical demonstration of the NK(1) tachykinin receptor on muscle and epithelia in guinea pig intestine.
OBJECTIVE
Previous immunohistochemical studies failed to reveal neurokinin (NK)(1) tachykinin receptors on intestinal muscle, despite convincing pharmacologic data indicating their presence. This study aimed to apply optimal immunohistochemical methods to reveal the receptors.


METHODS
NK(1)-receptor immunoreactivity was examined by confocal microscopy in tissue incubated with or without 10(-7) mol/L substance P (SP), 10(-7) mol/L SP plus 10(-6) mol/L NK(1) receptor antagonist (CP99994), or with fluorescent cyanine 3.18 (Cy3) SP.


RESULTS
Without incubation, NK(1)-receptor immunoreactivity was strong on muscle of the rectum and distal colon and weak in proximal colon and small intestine. NK(1) receptor was located on the surface of muscle cells in all gut regions. Exposure to SP increased the intensity of immunoreactivity, and the receptor moved into the cytoplasm. Mobilization of the receptor by SP was blocked by the NK(1)-receptor antagonist CP99994. Cy3-SP was internalized by muscle cells and colocalized with the receptor. NK(1)-receptor immunoreactivity occurred on crypt epithelial cells in the small intestine and the base of glands in the proximal colon.


CONCLUSIONS
The NK(1) receptor occurs on the external muscle throughout the small and large intestines. SP binds and triggers NK(1)-receptor aggregation and internalization in the muscle.
Department of Gastroenterology, Murdoch Children's Research Institute, Parkville, Victoria 3052, Australia. southwell@murdoch.rch.unimelb.edu.au
B R
BR
Southwell
J B
JB
Furness
D000818:Animals; D002232:Carbocyanines / Q000378:metabolism / Q000494:pharmacology; D003106:Colon / Q000166:cytology / Q000294:innervation; D004705:Endocytosis / Q000187:drug effects; D004847:Epithelial Cells / Q000737:chemistry / Q000378:metabolism; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism / Q000494:pharmacology; D006168:Guinea Pigs; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000737:chemistry* / Q000166:cytology / Q000294:innervation; D007421:Intestine, Small / Q000166:cytology / Q000294:innervation; D008297:Male; D009130:Muscle, Smooth / Q000737:chemistry* / Q000294:innervation; D009412:Nerve Fibers / Q000737:chemistry; D064729:Neurokinin-1 Receptor Antagonists; D010880:Piperidines / Q000494:pharmacology; D018040:Receptors, Neurokinin-1 / Q000032:analysis* / Q000378:metabolism; D018041:Receptors, Neurokinin-2 / Q000032:analysis / Q000378:metabolism; D018042:Receptors, Neurokinin-3 / Q000032:analysis / Q000378:metabolism; D012007:Rectum / Q000187:drug effects / Q000502:physiology; D013373:Substance P / Q000494:pharmacology
D002232:Carbocyanines; D005456:Fluorescent Dyes; D064729:Neurokinin-1 Receptor Antagonists; D010880:Piperidines; D018040:Receptors, Neurokinin-1; D018041:Receptors, Neurokinin-2; D018042:Receptors, Neurokinin-3; C089187:cyanine dye 3; C080755:3-(2-methoxybenzylamino)-2-phenylpiperidine; D013373:Substance P