Met-enkephalin characterization in the cochlea: high-performance liquid chromatography and immunoelectron microscopy.

The present paper extends and refines previous observations of enkephalin-like immunoreactivity in the guinea-pig cochlea. Firstly, Met-enkephalin was identified and a quantitative evaluation was made by combining high-performance liquid chromatography (HPLC) and a specific radioimmunoassay. Both the antibody specificity and the HPLC purification allowed us to demonstrate the co-existence, in the cochlea, of at least 3 opioid peptides: Met-enkephalin, Leu-enkephalin and Met-enkephalin-Arg6-Phe7. Secondly, a pre-embedding immunoperoxidase technique was used on whole or dissected cochleas. Immunoreactivity was localized in efferent fibers (coming from the brainstem) in the inner spiral bundle, tunnel spiral bundle and intraganglionic spiral bundle. In the inner spiral bundle vesiculated Met-enkephalin-immunoreactive fibers could be seen synapsing with afferent auditory dendrites. It is hypothesized that these Met-enkephalin immunoreactive fibers (belonging to the lateral efferent system) could be responsible for an inhibitory effect upon the gross cochlear action potential.

Monoclonal antibodies against Met-enkephalin as probe in the central nervous system.

Peptides with transmitter-like properties have been found in many brain areas. Immunochemical techniques have contributed most to clarification of the function and the pathway of these substances in neuronal systems. In this paper we report the production of 4 monoclonal antibodies against Met-enkephalin and their use in studying this peptide in rat cervical cord. Two of the antibodies recognize the COOH-terminus part of the Met-enkephalin, and do not cross-react with other known peptides. The other two antibodies are mainly directed against the NH2-terminus part of the peptide. Specific interactions of these monoclonal antibodies with regions of rat cervical cord were shown by immunochemistry techniques.