Calcium antagonists in the treatment of experimental cerebral ischemia

Calcium ion functions widely as an intracellular messenger and regulator. Intracellular calcium dyshomeostasis occurs during hypoxic/ischemic cell injury, and pharmacological antagonism of calcium entry into neurons has been considered to be of potential therapeutic value. Calcium antagonists, in addition, tend to improve cerebral perfusion of both the normal and abnormal (post-ischemic) brain. Studies of these agents have shown variable degrees of cerebroprotection in focal and global ischemia models. (S)-Emopamil is a phenylalkylamine-type calcium channel blocker which also exhibits stereoselective antagonism of the serotonin S2 receptor and has excellent blood-brain barrier penetrability. Protection of hippocampal CA1 neurons has been demonstrated with pre-ischemic administration of (S)-emopamil in global ischemia models. Our laboratory has compared the efficacy of pre- vs. post-ischemic (S)-emopamil treatment on neuronal necrosis resulting from 10 min of transient normothermic global ischemia in the rat. (S)-Emopamil pre-treatment, 20 mg/kg i.p., 30 min prior to ischemia, with a second dose 2.5 h later, resulted in 1.8-2.4 fold increases in numbers of surviving CA1 pyramidal neurons. Post-ischemic administration was ineffective. Intracerebral microdialysis has revealed a partial attenuation of dopamine release with pre-ischemic (S)-emopamil administration. In focal cerebral ischemia (middle cerebral artery occlusion in the rat), our laboratory has demonstrated a marked reduction in cortical infarct volume with (S)-emopamil pre- or post-treatment.(ABSTRACT TRUNCATED AT 250 WORDS)