Effect of seizures and diuretics on the osmolality of the cerebrospinal fluid.

There was a significant increase in the osmolality of the cerebrospinal fluid (CSF) of the anesthetized rats after treatment with 80 mg/kg (but not 39 mg/kg) furosemide and 1 g/kg of mannitol, but not during seizures induced by kainic acid. Furosemide (10 mg/kg) blocked seizure activity by kainic acid, while mannitol (1 g/kg) did not. The results suggest that the antiepileptic effect of furosemide is due to a direct CNS effect not related to a change in CSF osmolality.