Nematosomes in the Rat Trigeminal Ganglion

The fine structure of a "new" cytoplasmic inclusion in sympathetic neurons of adult rats has recently been described (2) . This inclusion was called a nematosome ("threadlike") and consisted of a convoluted network of electron-opaque strands embedded in a less dense matrix : it averaged 0.9 u in diameter. Morphological similarities between nematosomes, nucleoli, and synaptic material led to the suggestion that a nematosome might be an intermediary in the transfer of nuclear-derived substance to the subsynaptic specializations occurring beneath the neuronal membrane (2) . The present communication describes the presence of a morphologically similar inclusion in the cell bodies of sensory neurons of the rat trigeminal ganglion . This inclusion will also be referred to as a nematosome . The observations were made on tissue examined in the electron microscope during the course of studies of light and dark trigeminal neurons (6) and studies of the importance of fixative osmolality in preserving neuronal fine structure (7) .