Association of [3H]zacopride with 5-HT3 binding sites.
An assay was developed for [3H]zacopride binding to 5-HT3 specific sites in membranes from rabbit ileum muscularis. The binding was rapid, saturable, reversible, salt-insensitive, unaffected by pH between 6.5 and 9.5, and of high affinity (apparent KD = 0.65 +/- 0.15 nM). ICS 205-930, a potent 5-HT3 antagonist that inhibited competitively, was utilized to define 5-HT3 specific binding. Other 5-HT3 antagonists and agonists, although exhibiting marked differences in potency, were also effective inhibitors; whereas, antagonists of other classes of serotonin receptors, guanyl nucleotides and numerous receptor-specific ligands, including peptide hormones, were inactive. Vagus nerve exhibited the greatest amount of 5-HT3 specific binding amongst rabbit tissues and virtually all of the [3H]zacopride was bound to 5-HT3 binding sites. In rabbit, rat and ferret a fairly uniform distribution of 5-HT3 binding sites was observed along the muscularis of the small bowel. [3H]Zacopride is a high-affinity ligand for detecting 5-HT3 binding sites and rabbit small bowel muscularis membranes are a sensitive system for evaluating the potency of 5-HT3 antagonists or agonists.
Pinkus
L M
LM
Department of Molecular Biology, A.H. Robins Research Laboratories, Richmond, Virginia 23261-6609.
Sarbin
N S
NS
Barefoot
D S
DS
Gordon
J C
JC
D000818:Animals; D001549:Benzamides / Q000378:metabolism*; D001643:Bridged Bicyclo Compounds / Q000378:metabolism*; D019086:Bridged Bicyclo Compounds, Heterocyclic; D001952:Bridged-Ring Compounds / Q000378:metabolism*; D005289:Ferrets; D006863:Hydrogen-Ion Concentration; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000378:metabolism*; D013045:Species Specificity
D001549:Benzamides; D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D001952:Bridged-Ring Compounds; D010455:Peptides; D011985:Receptors, Serotonin; C055971:zacopride