CHANGE OF PHOSPHOTYROSINE IMMUNOREACTIVITY ON MICROGLIA IN THE RAT SUBSTANTIA-NIGRA FOLLOWING STRIATAL ISCHEMIC-INJURY

Using immunohistochemistry, we investigated changes in phosphotyrosine (P-Tyr) immunoreactivity on the microglia of the rat substantia nigra (SN) following striatal ischemic injury produced by transient middle cerebral artery (MCA) occlusion. Anterograde axonal degeneration in th e SN due to striatal ischemic injury was detected by depletion of calc ineurin immunoreactivity in that region from 1 day after operation. Fr om 3 days to 1 month (the longest period examined in this study) after MCA occlusion, there was a significant increase in P-Tyr immunoreacti vity in the SN ipsilateral to the MCA occlusion. Also, light microscop ic observation showed that the microglia exhibited an increased immuno reactivity for P-Tyr and characteristic morphological changes in the i psilateral SN. The present results indicate that a signal transducing cascade(s) associated with tyrosine phosphorylation may be involved in the activation of the microglia in the SN responding to anterograde d egeneration of the striatonigral pathway. (C) 1995 Wiley-Liss, Inc.