5-hydroxytryptamine injected intraventricularly fails to influence the brain water content.

Measurement of the content of brain water and electrolytes after the intraventricular administration of 5-hydroxytryptamine in rats, with and without exposure to osmotic stress, failed to show water accumulation in the brain parenchyma. It is suggested that elevation of serotonin in the cerebrospinal fluid--resembling pathological situations such as subarachnoid hemorrhage--does not play a primary role in brain edema formation.