ULTRASTRUCTURAL EXAMINATION OF B-50(GAP-43) IMMUNOREACTIVITY IN RAT JEJUNAL VILLI

The lamina propria of rat jejunum is densely innervated with nerve fib res extending to the tips of the villi. A large number of these nerve fibres were previously shown to be B-50-immunoreactive at the light mi croscope level, whereas neurofilament immunoreactivity was found to be sparse in the mucosa. In this study we used immunoelectron microscopy to determine what proportion of nerve fibres in the lamina propria ex press B-50. Jejuna from male Lewis rats were immunolabelled for B-50 a nd neurofilament proteins. For electron microscopy, postembedding immu nogold-silver techniques and LR White embedded tissues were used. Ligh t microscopical immunostaining was performed by the streptavidin-bioti n-peroxidase technique on deparaffinized tissue sections. We found tha t all ultrastructurally identifiable nerve profiles in jejunum were B- 50 immunoreactive. Immunoelectron microscopy for neurofilament protein s failed to label fibres in the villi, whereas myelinated nerves in to ngue sections processed in parallel (positive controls) were strongly neurofilament-protein-immunoreactive. The dominant B-50-positive and n eurofilament-protein-negative phenotype supports the hypothesis of ong oing modelling or plasticity of intestinal mucosal nerves.