Ultrastructural localisation of intramuscular expression of BDNF mRNA by silver-gold intensified non-radioactive in situ hybridisation.

A non-radioactive in situ hybridisation method is described for the detection of low intramuscular levels of brain-derived neurotrophic factor (BDNF) mRNA at the electron microscope level. Application of high-grade silver-gold intensification of the diaminobenzidine end product of in situ hybridisation revealed that in adult rat muscle the constitutive expression of muscular BDNF is confined to the myofibres; satellite cells, Schwann cells, endothelial cells, fibroblasts or axons do not appear to contribute to BDNF production in normal muscle. Although muscular BDNF is a neurotrophic factor for innervating motoneurons and supposedly released only at the motor endplates, the production of BDNF mRNA appears to occur along the entire length of the myofibres and is not confined to nuclei in the postsynaptic regions.