Inhibition of cyclic AMP-dependent protein kinase in the acute phase of focal cerebral ischemia in the rat

• Published in: Neuroscience 1999-09, Vol.94 (2), p.361-371
• Main Authors: Tanaka, K., Nogawa, S., Nagata, E., Suzuki, S., Dembo, T., Kosakai, A., Fukuuchi, Y.
• Format: Article
• Language: English
• Subjects: Animals; Antipyrine - analogs & derivatives; Antipyrine - pharmacokinetics; Autoradiography; Biological and medical sciences; Brain - blood supply; Brain - enzymology; Brain - physiopathology; Carbon Radioisotopes; Caudate Nucleus - physiopathology; Cerebral Cortex - physiopathology; cerebral ischemia; Cerebrovascular Circulation; cyclic AMP; Cyclic AMP - metabolism; cyclic AMP-dependent protein kinase; Cyclic AMP-Dependent Protein Kinases - antagonists & inhibitors; focal ischemia; Ischemic Attack, Transient - enzymology; Ischemic Attack, Transient - physiopathology; Male; Medical sciences; Neurology; PKA; Putamen - physiopathology; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Reperfusion; signal transduction; Tritium; Vascular diseases and vascular malformations of the nervous system
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(99)00314-0

Binding of cyclic AMP to the regulatory subunit of cyclic AMP-dependent protein kinase is an essential step in cyclic AMP-mediated intracellular signal transduction. In the present study, the binding capacity of cyclic AMP-dependent protein kinase for cyclic AMP was examined by autoradiography with local cerebral blood flow in focal cerebral ischemia in the rat, which was induced by occlusion of the middle cerebral artery using the intraluminal suture method. The binding capacity of cyclic AMP-dependent protein kinase and local cerebral blood flow were assessed by the in vitro [ 3H]cyclic AMP binding and the [ 14C]iodoantipyrine methods, respectively. At 3 h of occlusion, a significant reduction in the binding of cyclic AMP-dependent protein kinase to cyclic AMP was already noted in the lateral region of the caudate–putamen and the parietal cortex. Between three and five hours of occlusion, the area with reduced cyclic AMP binding was significantly expanded to the peri-ischemic regions including the frontal cortex and the medial region of the caudate–putamen. The threshold in local cerebral blood flow for reduced cyclic AMP binding was clearly noted at 5 h of ischemia, and was 45 ml/100 g per min in the cerebral cortices, and 38 ml/100 g per min in the caudate–putamen, respectively. No threshold was noted at 3 h of ischemia, since cyclic AMP binding showed a large variation ranging from reduced to normal values even when local cerebral blood flow was below 20 ml/100 g per min. Recirculation for 3.5 h following 1.5 h of ischemia restored the normal cyclic AMP binding in the cerebral cortices, but failed to normalize cyclic AMP binding in the caudate–putamen despite good recovery of local cerebral blood flow. Western blot analysis suggested that this reduction in cyclic AMP binding was not due to loss or degradation of the subunit protein of cyclic AMP-dependent protein kinase, and may therefore have resulted from conformational changes in the protein. A significant increase in cyclic AMP binding was noted after recirculation in the non-ischemic regions such as the frontal and the cingulate cortices on the occluded side and in the contralateral cortices. These data indicate that cyclic AMP-mediated signal transduction in the brain tissue may be very susceptible to ischemic stress, and the region of disrupted signal transduction may expand progressively from the ischemic core to peri-ischemic regions in the acute phase of ischemia. Such impairment of signal t