calcimycin and Cerebral-Infarction

Early deterioration and death after brain injury is often the result of oedema in the injured and peri-lesional tissue. So far, no pharmacotherapy is available that exhibits significant brain oedema-reducing efficacy in patients. We selected two low molecular weight compounds from different chemical classes, a triazole (1-[(2-chlorophenyl)diphenylmethyl]-1,2,3-triazole) and a cyclohexadiene (methyl 4-[4-chloro-3-(trifluoromethyl)phenyl]-6-methyl-3-oxo-1,4,7-tetrahydroisobenzofuran-5-carboxylate) to characterize their pharmacological properties on KCNN4 channels (intermediate/small conductance calcium-activated potassium channel, subfamily N, member 4) in vitro as well as in vivo. In vitro we replaced potassium by rubidium (Rb+) and determined Rb+ fluxes evoked by 10 micro m of the calcium ionophore A23187 on C6BU1 rat glioma cells. Compared with known KCNN4 blockers, such as clotrimazole (IC50=360 +/- 12 nm) and charybdotoxin (IC50=3.3 +/- 1.9 nm), the triazole and cyclohexadiene were considerably more potent than clotrimazole and displayed similar potencies (IC50=12.1 +/- 8.8 and 13.3 +/- 4.7 nm, respectively). In the rat acute subdural haematoma model, both the triazole and cyclohexadiene displayed reduction of brain water content (-26% at 0.3 mg/kg and -24% at 0.01 mg/kg) and reduction of the intracranial pressure (-46% at 0.1 mg/kg and -60% at 0.003 mg/kg) after 24 h when administered as a 4-h infusion immediately after brain injury. When infarct volumes were determined after 7 days, the triazole as well as the cyclohexadiene displayed strong neuroprotective efficacy (-52% infarct volume reduction at 1.2 mg/kg and -43% at 0.04 mg/kg, respectively). It is concluded that blockade of KCNN4 channels is a new pharmacological approach to attenuate acute brain damage caused by traumatic brain injury.

Topics: Animals; Brain Chemistry; Brain Edema; Brain Injuries; Calcimycin; Cell Line, Tumor; Cerebral Infarction; Charybdotoxin; Clotrimazole; DNA Primers; Erythrocytes; Glioma; Hematoma, Subdural; Humans; Intermediate-Conductance Calcium-Activated Potassium Channels; Potassium Channel Blockers; Potassium Channels, Calcium-Activated; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; Rubidium; Water

The protective effect of 2-(5-chloro-2-phenoxyanilino)-2-imidazoline [FR35447] on cerebral infarction was examined in animal models. FR35447 in p.o. doses of 1 mg/kg or more caused a marked reduction of arachidonate-induced cerebral infarction in rats. Since FR35447 (10(-6) M) inhibited platelet aggregation induced by adrenaline plus the divalent cation ionophore A23187, as did yohimbine (10(-6) M), the protective effect of FR35447 is presumed to be due to its blocking activity on the alpha 2 adrenoceptors of platelets. However, additional mechanisms appear to participate in the protective effect of FR35447 on cerebral infarction. A ten-day treatment with FR35447 in p.o. doses of 1 to 10 mg/kg/day decreased serum lipid peroxide levels in vitamin E deficient rats, suggesting that FR35447 may have free radical scavenging activity. Moreover, FR35447 (greater than or equal to 10(-5) M) increased red cell deformability. These effects of FR35447 suggest that it may be useful in preventing or treating cerebral infarction.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Calcimycin; Cardiovascular Agents; Cerebral Infarction; Epinephrine; Epoprostenol; Erythrocyte Deformability; Imidazoles; Lipid Peroxides; Male; Platelet Aggregation; Prazosin; Rats; Rats, Inbred Strains; Vitamin E Deficiency; Yohimbine