CGRP-immunoreactivity in Merkel cells and nonmyelinated nerve plexuses of dog skin.

In dog skin Merkel cells, calcitonin gene-related peptide (CGRP) immunoreactivity was consistently encountered at the subcellular dense-core granule region. The immunogold particles used as a marker for CGRP, were located specifically in and around the dense-core granules. They were also found in the surrounding cytoplasm close to the dense-core granules. Nerve terminals supplying the Merkel cell were CGRP-negative. CGRP-immunoreactive nonmyelinated nerve fibres were also found in the same specimen. These nonmyelinated nerve fibres were ensheathed by Schwann cell cytoplasm. The gold particles were only located in the dense-core granules of the axis cylinders. It is concluded that a CGRP-like substance predominantly accumulates in the dense-core granules of dog Merkel cells as well as in cutaneous nonmyelinated fibres.