AJP - Gastrointestinal and Liver Physiology, Vol 266, Issue 1 106-G112, Copyright © 1994 by American Physiological Society

ARTICLES

Characterization of galanin receptor in canine small intestinal circular muscle synaptosomes

C. K. Chen, T. J. McDonald and E. E. Daniel
Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.

We used 125I-galanin (porcine) as ligand to study the galanin receptors in circular muscle and deep muscular plexus from canine small intestine. Specific binding sites were found in both nerve and muscle membranes. On synaptosomal membranes, the equilibrium binding study showed a high-affinity (dissociation constant, Kd = 1.1 +/- 0.13 nM; maximum binding capacity, Bmax = 244 +/- 2.1 fmol/mg) binding site. The specific binding of 125I-galanin to nerve membrane was inhibited by galanin or NH2-terminal galanin fragments but not by the COOH-terminal fragment. Computer analysis suggested a two-site model (inhibitor constants, Ki1 = 0.02 +/- 0.005 nM and Ki2 = 1.05 +/- 0.3 nM) for competition by galanin-(1-29). Kinetic and competition studies using guanosine 5'-O-(3-thiotriphosphate) or pertussis toxin (PTX) suggested that the high-affinity binding site involved a PTX-sensitive G protein which acted to slow dissociation of bound galanin from the receptor. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the galanin receptor complex revealed a radioactive band at 50 kDa. We conclude that, in canine small intestine, galanin may act as an inhibitory neuromodulator by a PTX-sensitive G protein-coupled interaction of galanin and its specific receptor on enteric nerve synaptosomes.

This article has been cited by other articles:

				S. Yamato, I. Hirano, and R. K. Goyal Effect of galanin and galanin antagonists on peristalsis in esophageal smooth muscle in the opossum Am J Physiol Gastrointest Liver Physiol, October 1, 2000; 279(4): G719 - G725. [Abstract] [Full Text] [PDF]