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- Title
Detection of the 5-HT<sub>1 A</sub> receptor and 5-HT<sub>1 A</sub> receptor mRNA in the rat bowel and pancreas: Comparison with 5-HT<sub>1 P</sub>receptors.
- Authors
Kirchgessner, A. L.; Liu, M.-T.; Howard, M. J.; Gershon, M. D.
- Abstract
We tested the hypothesis that the rat bowel and pancreas contain 5-HT1A receptors. 3H-8-hydroxy-2-(di-n-propylamino) tetralin (3H-8-OH-DPAT) was used as a radioligand. Binding of 3H-8-OH-DPAT to membranes derived from the myenteric plexus and the pancreas was investigated by rapid filtration. Alternatively, radioautography was employed to locate 3H-8-OH-DPAT binding sites in frozen sections of unfixed bowel or pancreas. An excess of 5-HT (10 μM) was used to define nonspecific binding. Saturable, high affinity binding of 3H-8-OH-DPAT to enteric (Kd= 2.8 ± 1.1 nM; Bmax =83.8 ± 4.3 fmol/mgproteim) and pancreatic (Kd = 6.6 ± 1.3 nM; Bmax = 44 ± 2.2 fmol/mg protein) membranes was found. The binding of 3H-8-OH-DPAT to enteric and pancreatic membranes was inhibited by 8-OH-DPAT, NAN-190, and spiperone. In contrast, the binding of 3H-8-OH-DPAT to enteric and pancreatic membranes was not inhibited by 5-carboxyamidotryptamine, or by avariety of compounds known to bind to other subtypes of 5-HT receptor. Digoxigenin-labeled oligonucleotides were found to detect mRNA encoding the 5-HT1A receptor in a subset of neurons in myenteric and submucosal ganglia. In contrast, 5-HT1A mRNA was not found in the pancreas. Radioautography revealed that the highest density of 3H-8-OH-DPAT binding sites was found in the stomach. These sites were especially numerous in the lamina propria adjacent to gastric glands, and in myenteric ganglia. Pancreatic 5-HT1Areceptors were located on nerves, lymphoid tissue (especially the capsule of nodes), and on cells scattered in the pancreatic parenchyma. The concentration of 3H-8-OH-DPAT binding sites in the rat bowel and pancreas was less than that of 3H-5-HT binding sites; however, the distribution of 3H-8-OH-DPAT binding sites was similar to that of sites that bind 3H-5-HT. It is concluded that the rat gut and its extension in the pancreas contains 5-HT1A receptors. Many, if not all, of the nerve cells and processes that express 5-HT1A receptors express 5-HT1p receptors as well. The function of these receptors in the physiology of the entero-pancreatic innervation remains to be determined. © 1993 Wiley-Liss, Inc.
- Publication
Journal of Comparative Neurology, 1993, Vol 327, Issue 2, p233
- ISSN
0021-9967
- Publication type
Article
- DOI
10.1002/cne.903270206