Calcitonin gene-related peptide immunoreactivity in spinal spheroids in motor neuron disease

The spinal cords from seven autopsy cases of sporadic motor neuron disease (MND) and two controls were immunohistochemically examined using antibodies directed to calcitonin gene-related peptide (CGRP) and to neurofilament proteins (Nf). CGRP immunoreactivity was observed in the posterior horns, especially in the laminae I and II, of all the spinal cords examined. In MND cases, in addition, a considerable number of spheroids in the anterior horns were labelled with the antibody. In some spheroids, their entire area was homogeneously immunostained, whereas in others the immunoreactivity was confined to a focal area(s) within the profile of the spheroids and between these two forms of staining several variations of the staining patterns were seen. The anti-Nf intensely and homogeneously labelled all spheroids and there was no appreciable difference in the Nf-immunoreactive pattern between CGRP-positive and -negative spheroids. It is possible that the accumulation of CGRP in spheroids may result from entrapment of CGRP during the anterograde axonal transport, causing loss of CGRP at the neuromuscular junction and producing weakness and atrophy of the muscles.