Cerebrospinal fluid formation in rats and cats during treatment with timolol

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Abstract
The influence of timolol upon cerebrospinal fluid formation rate has been examined in rats by the measurement of 22Na+ entry into this fluid after 10, 100, or 1000 μg∙kg−1 i.v, and in cats by the dye-dilution measurement of new fluid formation after 30, or 3000 μg∙kg−1 i.v., or 250 μg∙mL−1 in ventricular perfusate. In rats no change from control rates occurred. In the cats there appeared to be no effect of intraventricular timolol; however, a significant decrease of ~ 25% in the mean flow rate was seen after 40 min when drug was given i.v. at either dose level. A time study showed that no further decrease occurred within 5 h and that the observed decrease continued for at least 3 h. These findings are of interest in view of the ability of topical, intraocular, and i.v. timolol to reduce aqueous humor formation rate.