[Anti-migraine effects of lomerizine]

Lomerizine, a novel Ca2+ channel blocker, is under development as an anti-migraine drug. We examined the effects on spreading depression (SD) induced by a brief period of hypoxia (40 to 60 sec) in rat hippocampal slices, the cortical hypoperfusion and cortical c-Fos-like immunoreactivity that follow KCl-induced SD in anesthetized rats as compared with those of flunarizine. Extracellular recording was made from the CA1 subfield. The latency of initiated SD was examined. Lomerizine (1 and 10 nM) and flunarizine (1 microM) significantly prolonged the latency in a concentration-dependent manner. After KCl application to the cortex, cerebral blood flow monitored by the laser Doppler flowmetry was approximately 20 to 30% below baseline for at least 60 min. Lomerizine (0.3 and 1 mg/kg, i.v.) and flunarizine (1 and 3 mg/kg, i.v.) administered 5 min before KCl application inhibited the cortical hypoperfusion that followed KCl application. c-Fos-like immunoreactivity, an indicator of neuronal activation, was detected in the ipsilateral, but not in the contralateral frontoparietal cortex 2 hr after KCl application. Lomerizine (3-30 mg/kg, p.o.) and flunarizine (30 mg/kg, p.o.) significantly attenuated the expression of c-Fos-like immunoreactivity in the ipsilateral frontoparietal cortex. Lomerizine was 3 to 1000 times more potent than flunarizine in the above SD models. These findings suggest that the inhibitory effects of lomerizine and flunarizine on the interval between the initiated and subsequent spontaneous SDs, the cortical hypoperfusion and expression of c-Fos-like immunoreactivity induced by SD are mediated via the effects of Ca2+ entry blockade, which may include an increase in cerebral blood flow and the prevention of excessive Ca2+ influx into brain cells.