Anti-idiotypic antibodies as a tool for cytochemical identification of substance P receptors in the central nervous system

Anti-idiotypic antibodies may serve as valuable probes for cytological identification of peptide receptors in the CNS. We have previously described the preparation of anti-substance P (SP) anti-idiotypic antibodies (anti-Id Ab) and have shown that they recognize SP receptors. These anti-Id Ab can be used in cytology to label SP receptors in CNS. We chose rat cervical spinal cord as a model because SP is present in large amounts in the dorsal and ventral horns, where it is implicated in pain and in motor function, respectively. After application of an indirect immunoperoxidase technique to tissue sections from perfused animals, immunolabeling was seen in the two superficial layers of the dorsal horn, the area surrounding the central canal, extending along the white matter in lamina VII, and in part of the ventral horn. This localization is in accordance with the classical distribution of SP receptors as seen by autoradiography with labeled SP. In the light of control experiments, as well as of biochemical and pharmacological arguments, we discuss the specificity of the immunolabeling. We conclude that anti-Id Ab recognize NK-P receptors, although crossreaction with NK-A or NK-B receptors cannot be totally ruled out.