Conservation of antigenic epitopes of the inhibitory glycine receptor in rodent and goldfish CNS.

Monoclonal antibodies against the inhibitory glycine receptor of rat spinal cord were used to identify corresponding receptor polypeptides in goldfish CNS. Both Western blot analysis and quantitative receptor immunoassays revealed crossreacting antigens in goldfish brain membranes. A polypeptide of 46 kDa molecular weight is immunologically related to the 48 kDa alpha subunit of the mammalian receptor. Similarly, a large receptor-associated protein of 93 kDa is present both in goldfish and mammals. Throughout the goldfish CNS, glycine-displaceable [3H]strychnine binding codistributes with the alpha subunit protein as determined immunologically. Glycine receptor contents were highest in goldfish medulla oblongata, medium in optic tectum and mesencephalon, whereas little or no receptor was detected in cerebellum, olfactory bulb, and spinal cord. Immunohistochemistry confirmed that the alpha subunit antigen and the 93 kDa protein were located in the plasma membrane of neurons and concentrated in small clusters found on the soma and dendrites. These data indicate that immunological properties and cellular distribution of glycine receptors are conserved from fish to mammals.