Polyclonal antibodies to the glycine receptor antagonist strychnine

Polyclonal antibodies have been raised in rabbits against the glycine receptor antagonist strychnine, coupled through a 2-amino substituent to the antigenic protein key-hole limpet haemocyanin. Strychnine binding of the predominantly immunoglobulin G (IgG) class of antibodies was measured by incubation with [3H]strychnine, followed by adsorption of IgG onto Staphylococcus aureus cells and filtration through glass-fibre filters under vacuum. Only strychnine and structurally related alkaloids or derivatives were able to inhibit [3H]strychnine binding to the IgG. A significant rank correlation was found between the potencies of these compounds to inhibit [3H]strychnine binding to the antibodies and to the glycine receptor in mouse spinal cord membranes. In contrast, preincubation of strychnine antibodies with a variety of ligands at other neurotransmitter, drug, or hormone receptors in the CNS (at 10(-4) M) failed to inhibit binding significantly. The failure of glycine to inhibit strychnine antibody binding is consistent with previous suggestions that the recognition sites for this amino acid on the CNS receptor may be conformationally distinct from those for the antagonist alkaloid. Strychnine antibodies may now help in the identification and purification of possible endogenous ligands at this alkaloid binding site in the CNS.