Ca-blocking action of stereoisomers of CI-951, (+)-CI-951 (NC-1500) and (-)-CI-951 in the isolated muscle preparations.

1. Stereoselectivity of CI-951 in Ca-entry blocking activity was tested in guinea pig taenia caecum and urinary bladder and rabbit thoracic aorta and basilar artery. 2. NC-1500 ((+)-CI-951) and (-)-CI-951 had a selectivity to the basilar artery. 3. NC-1500 ((+)-CI-951) was about 6-16 times as potent as (-)-CI-951. 4. These results suggest that NC-1500 ((+)-CI-951) may be considered a cerebral vasodilator and have potential usefulness as a therapeutic drug.