Passage of intravenously administered tubocurarine into the liquor space in man and dog.

1. In anaesthetized patients under controlled respiration, samples of lumbar cerebrospinal fluid were withdrawn 15 and 60 min after an intravenous injection of 30 mg tubocurarine. When tested on the frog rectus muscle preparation contracted by acetylcholine, they exerted curare-like activity which corresponded to between 0.05 and 0.33 mug/ml tubocurarine.2. In dogs anaesthetized with pentobarbitone sodium and artificially ventilated, two procedures were adopted to find out if tubocurarine passes into the liquor space after an intravenous injection of 0.3 or 3 mg/kg and during its intravenous infusion at a rate of 10 (mug/kg)/minute. Either samples of cisternal cerebrospinal fluid (c.s.f.) were collected, or different regions of the liquor space were perfused with artificial c.s.f. and the effluent was collected. The samples of c.s.f. and the effluent were assayed for curare-like activity on the frog rectus muscle.3. After the intravenous injection of tubocurarine samples of cisternal effluent collected during perfusion from lateral ventricle to cisterna exerted curare-like activity. It corresponded to 20 ng/min tubocurarine in the sample collected during the first 15 min after the injection of 0.3 mg/kg and to 40-60 ng/min in the samples collected up to 2 h after the injection of 3 mg/kg.4. During intravenous infusion of tubocurarine the cisternal c.s.f. as well as the effluent from the perfused regions of the liquor space exhibited curare-like activity. Expressed in equivalents of tubocurarine, the activity in the cisternal c.s.f. ranged from between 0.1 and 0.75 mug/ml. On perfusion from lateral ventricle to aqueduct or cisterna, the activity ranged from between 3 and 25 ng/min in the aqueductal and from between 4 and 40 ng/min in the cisternal effluent. On perfusion from the lumbar-spinal subarachnoid space to cisterna it ranged from between 6 and 55 ng/min in the cisternal effluent.