Effects of a calcium antagonist, lacidipine, on experimental focal cerebral ischemia in rats.

We investigated the effects of lacidipine on focal cerebral ischemia in rats, and these effects were compared with those of nicardipine. Drugs were administered orally 5 min after middle cerebral artery occlusion (MCAO). Neurological scores as described by Bederson et al. (Stroke 17, 472-476, 1986) and cerebral infarct size (CIS) determined by the 2,3,5-triphenyltetrazolium chloride staining method were measured 24 hr after MCAO. Cerebral blood flow (CBF) and energy metabolites were determined by the hydrogen clearance method and an enzymatic method, respectively. In the drug-untreated group, we observed low-CBF of approximate 13 ml/100 g/min during 0.5-6 hr of occlusion and extensive cerebral infarction associated with severe neurologic deficits (ND). Lacidipine at 1 and 3 mg/kg, although it lowered blood pressure, improved low-CBF to approximate 20 ml/100 g/min during 1.5-6 hr of occlusion and increased tissue levels of ATP 6 hr after MCAO in a dose-dependent manner. Nicardipine at 30 mg/kg also improved low-CBF and increased tissue levels of ATP significantly. However, the improvement of low-CBF by nicardipine was transient. Lacidipine at 3 mg/kg reduced CIS and ameliorated ND significantly. In contrast, nicardipine at 30 mg/kg could not ameliorate ND in spite of a significant reduction of CIS similar to that of lacidipine (3 mg/kg). These results suggest that the improvement of focal cerebral ischemia by lacidipine may be partly due to long-lasting improvement of collateral blood supply to the ischemic area.