Activity of peripheral sympathetic efferent nerves in experimental subarachnoid haemorrhage. Part II: Observations during the "early vasospasm" period.

The efferent activity of the vertebral, cardiac and renal sympathetic nerves was recorded during the so-called "early vasospasm" period, 25-30 minutes after experimentally induced subarachnoid haemorrhage. Experiments were performed on 51 cats with methods described in Part I of our publication. The animals were held either in a sphynx-like position (Pos. I), or in head-down position (Pos. II), when the level of the cisterna magna was 2-3 cm below the level of the spinal cord, facilitating the injected blood to flow in to, and remain at the base of the brain. According to our results during the "early vasospasm" period, we could not observe such changes in the sympathetic efferent activity, which could be specific for this period. With the gradual decrease in the intracranial pressure, the sympathetic overactivity ceased, and in most cases the level of activity was similar to that of the preinjection period. Our results also indicate that because of the remarkable variability of the activity of the renal sympathetic nerve during the intracranial pressure elevation, recording the activity of one sympathetic nerve only may give misleading results concerning the activity of the whole sympathetic system.