Sympathetic nervous control of cerebrospinal fluid production in experimental obstructive hydrocephalus

Hydrocephalus was induced in rabbits by cisternal injection of kaolin (0.5 ml of a 30 g/100 ml solution of hydrated aluminium silicate). The rate of bulk production of cerebrospinal fluid (CSF) was measured with a modified Pappenheimer [14C]inulin dilution technique in a ventriculoventricular perfusion system 3 days and 3 weeks after treatment. In the acute state of high-pressure hydrocephalus, CSF formation was reduced to almost one-half normal. Bilateral electrical stimulation of the cervical sympathetic nerves lowered the production rate by another 18%, with only an insignificant tendency to normalization after cessation of stimulation. In the chronic state of low-pressure hydrocephalus at 3 weeks after the kaolin injection, the rate of CSF formation was of the same magnitude as in animals studied after 3 days. However, sympathetic nerve stimulation now reduced the production rate by a further 39%, and prestimulation values were almost restored within 1 h after termination of stimulation. Thus, cranial sympathetic stimulation was very effective in reducing CSF formation in the chronic stage of low-pressure hydrocephalus. during acute high-pressure hydrocephalus, the sympathetic defence mechanisms were probably already recruited to such an extent that electrical activation of the sympathetic nerves was not able to further affect significantly the rate of CSF formation.