An Immediate Light Microscopic Response of Neuronal Somata, Dendrites and Axons to Non-contusing Concussive Head Injury in the Rat

Sixteen rats were killed by transcardial perfusion fixation 1 min after a non-contusing concussive head injury, and seven rats 1 day later. In each of the "1-min" animals Golgi-like neurons and long axonal segments scattered in various proportions among unstained neurons and axons were demonstrated by a new silver method both near to and far from the impact site in a parenchymal environment unaffected by contusion. The silver-stained neurons, dendrites and axons were considered to have been damaged by the trauma because they were consistently absent from control brains. In the "1-day" brains silver-stained dendrites and axons had a beaded appearance, indicating an advanced stage of morphopathological damage. From details of these findings the following conclusions were drawn: (1) trauma can directly induce some kind of morphopathological damage in neurons which manifests itself in shrinkage of the soma and tortuosity of appendages as well as in type III argyrophilia; (2) different vulnerability of various brain areas is likely due to the inhomogeneity of the trauma-induced pressure wave propagating through the brain; and (3) the somato-dendritic and axonal domains of the neuron are selectively vulnerable to different values of the parameters of the intracranial pressure wave.