Glial cell responses in the adult rabbit dorsal motor vagal nucleus during axon reaction.

Following transection of the vagal nerve on the neck, a dramatic loss of neurons occurs in the dorsal motor vagal nucleus (DMV) of the adult rabbit. The present study describes the light and electron microscopical characteristics of the accompanying glial cell response. The number of microglial cells was considerably increased a few days after nerve injury and remained at a higher than normal level throughout almost the whole period examined. Astrocytes increased to some extent at a later post-operative stage. Ultrastructurally, microglial cells hypertrophied, surrounded degenerating neurons, and contained a variety of inclusion bodies, some of which appeared to be derived from degenerating neuroplasm. Astrocytes also hypertrophied, displayed numerous filaments and glycogen granules in their cytoplasm as well as a substantial number of heterogenous dense bodies. The findings indicate that the principal features of the glial cell response in the rabbit DMV is similar to previously described glial cell changes in other systems. However, the intensity in the response of astroglial cells in the DMV appears to be greater than usually observed, possibly reflecting the degenerative nature of the nerve cell body response.