Transient global ischemia in rats yields striatal projection neuron and interneuron loss resembling that in...

The various types of striatal projection neurons and interneurons show a differential pattern of loss in Huntington's disease (HD). Since striatal injury has been suggested to involve similar mechanisms in transient global brain ischemia and HD, we examined the possibility that the patterns of survival for striatal neurons after transient global ischemic damage to the striatum in rats resemble that in HD. The perikarya of specific types of striatal interneurons were identified by histochemical or immunohistochemical labeling while projection neuron abundance was assessed by cresyl violet staining. Projectionneuron survival was assessed by neurotransmitter immunolabeling of their efferent fibers in striatal target areas. The relative survival of neuron types was determined quantitatively within the region of ischemic damage, and the degree of fiber loss in striatal target areas was quantified by computer-assisted image analysis. We found that NADPHd(+) and cholinergic interneurons were largely unaffected, even in the striatal area of maximal damage. Parvalbumin interneurons, however, were as vulnerable as projection neurons. Among immunolabeled striatal projection systems, striatoentopeduncular fibers survived global ischemia better than did striatopallidal or striatonigral fibers. The order of vulnerability observed in this study among the striatal projection systems, and the resistance to damage shown by NADPHd(+) and cholinergic interneurons, is similar to that reported in HD. The high vulnerability of projection neurons and parvalbumin interneurons to global ischemia also resembles that seen in HD. Our results thus indicate that global ischemic damage to striatum in rat closely mimics HD in its neuronal selectivity, which supports the notion that the mechanisms of injury may be similar in both.