In view of the reported influence of 2-acetylamino-l,3,4,-thiadiazole-5-sulfonamide (Diamox) on formation of intraocular fluid( l ) , and the similarity between intraocular and cerebrospinal fluid (CSlF) systems, a series of experiments has been undertaken to determine the effect of this compound on CSF formation and intracranial pressure. In every instance, at least a 3-fold reduction in rate of CSF flow, or a decline of approximately 30% in intracranial pressure was observed following intravenous administration of 150 mg/kg soluble Diamoxt (acetazoleamide-sodium) .Cats and rabbits lightly anesthetized with sodium pentobarbital were placed on their sides with heads inclined slightly upwards from the horizontal. To measure CSF flow, a 22-gauge spinal needle was introduced into the cisterna magna and the rate at which drops of CSF appeared was recorded. The volume of each drop was found to be 0.04 cc. The CSF was collected in successive samples for periods of 15 minutes, or until sufficient fluid had accumulated for analysis of sodium, potassium and calcium in the flame spectrophotometer. In other ani-
Materials and methods.
Five pairs of matched horses were used to study the biochemical and haematological effects of a revised dosage schedule of phenylbutazone. One group of five horses received a phenylbutazone paste formulation daily for 12 days and a second group of five animals received a placebo preparation for a similar time. Some statistically significant differences were recorded from pretreatment levels in both groups of horses. These changes represented instability in baseline levels and could not be ascribed to phenylbutazone administration.
Previous studies (1, 2) concerned with the stabilization of erythrocytes to thermal labilization by anti-inflammatory drugs employed canine erythrocytes (RBC) . Lysergic acid diethylamide (LSD-2 5 ) and the steroidal or nonsteroidal anti-arthritic agents stabilized the RBC membrane while very few compounds representing other classes of pharmacologic agents were effective. The purpose of the present study was to determine, in part, the mechanism of stabilization and whetber RBC from species other than dog can be employed. A secondary purpose was to define the effectiveness of methysergide, an LSD-2 5 analog, and cyproheptadine, in order to ascertain whether antiserotonin agents, in general, can be detected in this system.Methods. Human blood (ACD) was collected from male volunteers. Rat (Sprague-Dawley) and guinea pig blood was obtained by decapitation; horse, goat, and rabbit blood was collected by venipuncture. Heparin was used as an anticoagulant except i'n human-blood. All blood was used on the day of collection. Until use it was stored at 2 to 5" in either an ice bath or refrigerator. Other procedures were similar to those previously described (1, 2). Anesthetized (sodium pentobarbital, 30 mgJkg iv) mongrel dogs of either sex weighing 10-14 kg were used. Whole blood was collected by catheterization of a carotid artery using heparin to prevent clotting. The blood was centrifuged at 650g for 15 min between 0-5". The volume of erythrocytes (RBC) was measured and reconstituted as a 40% (v/v) suspension with cold (0-5") 0.067 M sodium phosphate buffer, pH 7.4, containing 0.9% saline. Test
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