Abstract
To demonstrate patterns of vulnerability differences in hindbrain neurons at early stages of ischemia without recirculation periods, immunohistochemical study with antiserum to tubulin was performed on the brains of Mongolian gerbils obtained 10 min to 6 hours after occlusion of the basilar artery. The occlusion of this vessel in this animal has been demonstrated to produce moderate degree of ischemia in the cerebellum, brain stem and a part of thalamus. In terms of immunohistochemical changes in cytoplasmic tubulin, various types of selective vulnerability were observed in the hindbrain structures. Firstly, vulnerability was different among different neural structures; the vestibular nucleus was involved within 10 min after vascular occlusion and the cerebellar cortex between 30 min and 2 hours. The deeper portions of the cerebellar folia were affected more readily than the superficial portions. These regional differences in vulnerability may be related to the different threshold of the individual structure or to the different amount of residual blood flow. Secondly, vulnerability was different among different types of neurons even within the same neural tissue; large neurons in the vestibular nucleus were more susceptive than small neurons and all the large cells did not respond in the same manner. In addition to the conventional morphological typing of neurons, the chemical typing based on the neurotransmitter differences may provide some, but limited, value in evaluating vulnerability differences among certain types of neurons. Thirdly, vulnerability was different among different portions even within a single neuron; the dendrites of the cerebellar Purkinje cells lost tubulin immunoreactivity faster than the perikarya. Thus, the dendrites may be an early target of ischemic insult at least in some limited situations.
The present investigation demonstrated various types of selective vulnerability in the gerbil hindbrain structures. Although many of the causative factors responsible for the selectivity are currently only speculative or totaly unclear, this kind of immunohistochemical study is expected to provide an important clue for understanding the complex pathophysiology of ischemia in these important portions of the nervous system.
