A novel voltage-sensitive Na(+) and Ca(2+) channel blocker, NS-7, prevents suppression of cyclic AMP-dependent protein kinase and reduces infarct area in the acute phase of cerebral ischemia in rat.
Binding of cyclic AMP to the regulatory subunit of cyclic AMP-dependent protein kinase (PKA) is an essential step in cyclic AMP-mediated intracellular signal transduction. This binding is, however, rapidly inhibited in the acute phase of cerebral ischemia, indicating that the signal transduction via PKA is very vulnerable to ischemia, although this signal pathway is very important for neuronal survival in the brain. Several lines of evidence suggest that the activation of voltage-sensitive Na+ and Ca(2+) channels is an important mediator of acute ischemic brain damage. In the present study, therefore, we examined the effect of a novel Na+ and Ca(2+) channel blocker, NS-7 (4-(4-fluorophenyl)-2-methyl-6-(5-piperidinopentyloxy) pyrimidine hydrochloride), on changes in the binding activity of PKA to cyclic AMP in permanent focal cerebral ischemia, which was induced by occlusion of the middle cerebral artery by the intraluminal suture method for 5 h in the rat. NS-7 (1 mg/kg) or saline was intravenously infused 5 min after occlusion. The binding activity of PKA to cyclic AMP and local cerebral blood flow were assessed by the in vitro [(3)H]cyclic AMP binding and the [(14)C]iodoantipyrine methods, respectively. NS-7 significantly suppressed inhibition of the binding activity of PKA to cyclic AMP in the ischemic regions such as the frontal and parietal cortices and the medial region of the caudate-putamen without affecting cerebral blood flow or arterial blood pressure. Infarct area measured in the brain slices stained with cresyl violet was significantly smaller in animals treated with NS-7 than in those treated with saline. Blockade of voltage-sensitive Na+ and Ca(2+) channels by NS-7 was expected to reduce ischemia-induced depolarization and thus prevent a massive formation of free radicals, which is known to inhibit the binding activity of PKA to cyclic AMP. These data clearly indicate that NS-7 provides very efficient neuroprotection in the acute phase of cerebral ischemia, and sustains the normal function of PKA.
Tanaka
Kortaro
K
Department of Neurology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. kortaro@sc.itc.keio.ac.jp
Ito
Daisuke
D
Suzuki
Shigeaki
S
Dembo
Tomohisa
T
Kosakai
Arifumi
A
Fukuuchi
Yasuo
Y
D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000187:drug effects / Q000201:enzymology / Q000503:physiopathology; D002545:Brain Ischemia / Q000188:drug therapy* / Q000201:enzymology / Q000503:physiopathology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D002544:Cerebral Infarction / Q000188:drug therapy* / Q000201:enzymology / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000378:metabolism
C106144:4-(4-fluorophenyl)-2-methyl-6-(5-piperidinopentyloxy)pyrimidine hydrochloride; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D018696:Neuroprotective Agents; D011743:Pyrimidines; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases