Vasoconstriction of the basilar artery in rabbits: the vasoconstrictor activity of blood, CSF and blood-CSF mixtures incubated for varying periods of time.

After subarachnoid haemorrhage, the amount of blood in the subarachnoid space and the time elapsed since the haemorrhage seem important factors in predicting the occurrence of vasospasm. In this experiment we studied the responses of the rabbit basilar artery to acute topical application of samples of human cerebrospinal fluid (CSF), mixtures of blood and CSF incubated at 37 degrees C for 0 to 12 days. The degree and the duration of the vasoconstriction depended on the time of incubation and on the concentration of blood in the samples. Samples incubated for five and seven days caused severe and long-lasting vasoconstrictions. Samples incubated for 0, 1, 3, 8, 10 and 12 days caused slight or moderate and short-lasting vasoconstriction. Samples incubated for 5, 7, 8, and 10 days showed a linear relationship between the concentration of blood and the degree of constriction up to the blood-CSF ratio of 0.6 to 1 (blood content of 37.5%); further increases of blood concentration did not cause further vasoconstriction. This phenomenon may be related to the saturation of arterial receptors. The course of the vasoconstriction using samples with different blood concentrations suggests the existence of more vasoactive substances. This work seems to confirm the importance of blood concentration in the CSF and of time as factors governing the development of vasospasm.