Alteration of adenosine A1 receptor binding in the post-ischaemic rat brain

Chronological changes of adenosine A1 receptor binding of the rat brain were determined by in vitro [3H]cyclohexyladenosine (CHA) autoradiography after 90 min of middle cerebral artery (MCA) occlusion and after such occlusion followed by different periods of recirculation. One day after the ischaemia, [3H]CHA binding sites decreased significantly in the cerebral cortex (p < 0.05) and lateral segment of the caudate putamen (p < 0.01), both supplied by the occluded MCA; thereafter, the binding sites decreased progressively in those ischaemic foci. On the contrary, there was no alteration on day 1, but 3 days after ischaemic insult, a significant decrease of [3H]CHA binding sites was first detected in the ipsilateral thalamus and the substantia nigra, both areas which had not been directly affected by the original ischaemic insult. This post-ischaemic delayed phenomenon observed in the thalamus and the substantia nigra developed concurrently with 45Ca accumulation, which was studied in our previous study. Based on the present study, alteration of adenosine A1 receptor binding activities is involved not only in the ischaemic foci, but also in the remote areas associated neuroanatomically with the ischaemic foci. We suggest that multi-focal post-ischaemic alterations of adenosine A1 binding activities may exacerbate clinical symptoms of patients at a chronic stage of stroke.