Pharmacological properties of a new centrally acting muscle relaxant (NC-1200) in isolated muscle preparations.

1. Pharmacological properties of a new centrally acting muscle relaxant (NC-1200) were tested in isolated muscle preparations. 2. NC-1200 acted as a Ca-blocker in the guinea pig taenia caecum. The pA2-value was 5.67. 3. In the rabbit aorta, NC-1200 competed with serotonin at serotonin receptors and also shifted the concentration response curves of histamine and norepinephrine suggesting the possibility that NC-1200 interacted with histamine and norepinephrine receptors. The pA2-value of NC-1200 against serotonin was 6.02. 4. There was no evidence that NC-1200 interacted with drug-receptors in the muscles except the rabbit aorta. 5. The present results are similar to the previous findings that the properties of serotonin, histamine and norepinephrine receptors in the rabbit aorta were different from those in other muscles.