Upregulation of p75 neurotrophin receptor after stroke in mice does not contribute to differential vulnerability of striatal neurons

The survival of different neuron types and the expression of the p75 neurotrophin receptor (p75(NTR)) af ter focal cerebral ischemia were studied in the mouse striatum using immunocytochemical and histochemical techniques and stereological procedures. As assessed at 1 week after 30 min of middle cerebral artery occlusion, the order of vulnerability was projection neurons > parvalbumin-expressing interneurons > nitric oxide synthase-containing interneurons > cholinergic interneurons. Within the ischemic lesion, projection neurons were almost completely lost whereas cholinergic interneurons were spared. Calretinin-immunoreactive interneurons also seemed resistant to the insult. Expression of p75(NTR) was induced in cholinergic interneurons within the lesioned area, raising the possibility of a protective action. However, the number of cholinergic interneurons was unaffected in p75(NTR) knockout mice subjected to the same ischemic insult. These quantitative data demonstrate that striatal neurons in the mouse are differentially susceptible to ischemic damage and argue against a significant role of p75(NTR) for the high resistance of cholinergic interneurons. (C) 2001 Academic Press.