SM-6586

To test changes in the density of [3H] isradipine binding sites in rat brain membrane pretreated with amlodipine and to compare with those of nifedipine and (+) SM-6586 (methyl 1, 4-dihydro-2, 6-dimethyl-3-(3-(N-benzyl-N-methylaminomethyl)-1,2,4- oxadiazolyl-5-yl)-4-(3-nitrophenyl) pyridine-5-carboxylate).

The membrane-enriched fractions were prepared from rat brain. The brain membranes were preincubated with nifedipine (10 nmol L-1), amlodipine (1 mumol L-1) and SM-6586 (1 nmol L-1) or with no antagonists added for 45 min, and washing and centrifugation were performed 3 times. They were assayed with [3H]isradipine in incubation media. The Kd and Bmax values of the membrane fractions pretreated with the drugs were determined by Scatchard analysis.

The blockage of the [3H]isradipine binding sites induced by nifedipine was reversed by washing, enabling the low values of the specific binding sites to be observed. The blockages by amlodipine and SM-6586, on the other hand, were not readily reversed. No significant difference was found, however, between in the Kd walues of these drugs.

Amlodipine and SM-6586 are Ca2+ antagonists which dissociate slowly from the Ca2+ channel in membranes.

SM-6586 (SM) is a new derivative of dihydropyridine with potent calcium blocking activity and inhibitory activity of the Na+/H+ and Na+/Ca++ exchange transport. The effect of SM on survival rate, brain edema and metabolites was evaluated using two different models in spontaneously hypertensive rat (SHR). Global ischemia was induced by bilateral common carotid artery ligation (BLCL) and focal ischemia was induced by middle cerebral artery occlusion. The survival rate after BLCL was higher in the SM-treated group. The brain water content was lower, the ATP level was higher and lactate level was lower in the SM-treated group compared to the control group. In focal ischemia models, the SM-treated group showed a reduction of T1 relaxation time. The brain water content was significantly decreased in the SM-treated group. These results indicate that SM was effective in ameliorating the ischemic insult in global and focal cerebral ischemia models.