NEUROCHEMICAL CHANGES FOLLOWING OCCLUSION OF THE MIDDLE CEREBRAL-ARTERY IN RATS

We have developed a stroke model involving middle cerebral artery occl usion in the rat which elicits changes in cardiac and autonomic variab les that are similar to those observed clinically. It is likely that t hese neurogenic autonomic responses are mediated by changes in neurotr ansmitter systems subsequent to the stroke. This possibility was inves tigated by examining changes in immunohistochemical staining for tyros ine hydroxylase, neuropeptide Y, leu-enkephalin, neurotensin and dynor phin following middle cerebral artery occlusion in the rat. Computeriz ed image analysis was used to provide semi-quantitative measurements o f the changes. The ischemic region was centered primarily in the insul ar cortex. The results indicate that there are significant increases i n immunostaining for tyrosine hydroxylase and neuropeptide Y in the in sular cortex within the peri-infarct region. Neuropeptide Y staining w as also significantly increased in the basolateral nucleus of the amyg dala, ipsilateral to the middle cerebral artery occlusion, which did n ot appear to be included in the infarct. Leu-enkephalin, neurotensin a nd dynorphin staining was significantly elevated in the central nucleu s of the amygdala ipsilateral to the occlusion of the middle cerebral artery. These neurochemical changes are discussed as possible mechanis ms mediating the cardiac and autonomic consequences of stroke or as pa rt of a process to provide neuro-protection following focal cerebral i schemia.