Receptor for calcitonin gene-related peptide: Localization in the dorsal and ventral spinal cord

Although the distribution of calcitonin gene-related peptide has been exten sively studied in the spinal cord, little is known about the precise subcel lular localization of receptors for calcitonin gene-related peptide. The pr esent study was undertaken to localize calcitonin gene-related peptide rece ptors in both the dorsal and ventral horns of the rat spinal cord. Immunocy tochemical localization with specific monoclonal antibodies was performed a t the light and electron microscopic levels. Calcitonin gene-related peptid e receptor was expressed in neuronal but not glial elements. Discrete posts ynaptic localization of receptor for the calcitonin gene-related peptide wa s evident in the cells and dendrites of the superficial dorsal hem. Some of the terminal endings apposing the stained synapses formed the central term inals of glomerular complexes. The endings were scallop shaped (Type I), ty pical of primary afferent terminations. Other dorsal horn structures with p ostsynaptic labeling were contacted by dome-shaped or elongated axonal endi ngs. Presynaptic localization on some dorsal horn terminations may serve an autoreceptor function. Motoneurons, on the other hand, were contacted by a xonal terminals with presynaptic calcitonin gene-related peptide receptors. These data suggest that (i) dorsal horn neurons are capable of direct prima ry afferent, calcitonin gene-related peptide receptor-mediated interactions and (ii) neuronal terminals contacting motor horn cells can be influenced through presynaptic paracrine-like calcitonin gene-related peptide receptor -mediated interactions. Thus, calcitonin gene-related peptide can have mult iple modulatory effects on spinal cord neurons through site-specific recept ors. (C) 1999 IBRO. Published by Elsevier Science Ltd.