The Passage of Certain Substances Out of the Cerebrospinal Fluid

155

SUMMARY1. An operation on dogs for the implantation ofguide tubes to the lateral ventricle and cisterna magna and a method whereby the ventricular space can be repeatedly perfused in conscious and unrestrained animals are described.2. The characteristics of a recirculatory perfusion system were examined and the bulk formation and absorption of cerebrospinal fluid and the volume of the ventricular space perfused were derived from the concentrations achieved during the infusion of inulin into the system. 3. 5-hydroxyindol-3-ylacetic acid (5-HIAA), the acid metabolite of 5-hydroxytryptamine, and 3-methoxy-4-hydroxyphenylacetic acid (HVA), the main acid metabolite of dopamine, were demonstrated to be mainly removed from cerebrospinal fluid (c.s.f.) by an active transport system localized in the region of the fourth ventricle. 4. It was possible to inhibit the active transport of these acids from cerebrospinal fluid by pre-treating the dogs with probenecid.

Section: Discussionmentioning

confidence: 99%

“…That such an assumption was valid was demonstrated by Rall et al (1962) and by Pappenheimer & Heisey (1963). Pollay & Davson (1963) showed that the inulin dilution measurement of c.s.f. production in the rabbit was in good agreement with direct measurement.…”

Section: Discussionmentioning

confidence: 99%

The active transport of 5‐hydroxyindol‐3‐ylacetic acid and 3‐methoxy‐4‐hydroxyphenylacetic acid from a recirculatory perfusion system of the cerebral ventricles of the unanaesthetized dog

Ashcroft¹,

Dow²,

Moir³

1968

155

“…Maren, 1958;Fisher & Copenhaver, 1959;Giacobini, 1961), and the glia (Fisher & Copenhaver, 1959). Acetazolamide, at concentrations sufficient to inhibit carbonic anhydrase in vitro, causes a marked decrease in the bulk formation of CSF-an effect observed whether the acetazolamide is administered through the blood (Tschirgi et al 1954;Kister, 1956;Davson & Luck, 1957;Maren & Robinson, 1960;Oppelt et al 1963), or through the CSF (Pollay & Davson, 1963). These findings have strongly suggested inhibition by acetazolamide of secretory processes in the choroid plexus, and this interpretation has been confirmed by Welch's (1963) ingenious experiments demonstrating a marked-virtually complete-suppression of choroidplexus secretion after intravenous or intraventricular administration of acetazolamide.…”

Section: Discussionmentioning

confidence: 99%

“…Tschirgi, Frost & Taylor (1954); Fisher & Copenhaver (1959); Oppelt, Maren, Owens & Rall (1963); Pollay & Davson (1963). The present studies were designed to investigate certain aspects of this relation, not as it applies to CSF as a whole, but with respect specifically to the fluid formed by the choroid plexus of the lateral ventricle.…”

mentioning

confidence: 98%

Effects of Pco2 acetazolamide and ouabain on volume and composition of choroid‐plexus fluid.

Ames¹,

Higashi²,

Nesbett³

1965

127

A number of investigators have related CO2 metabolism to cerebrospinal-fluid (CSF) formation, e.g. Tschirgi, Frost & Taylor (1954); Fisher & Copenhaver (1959); Oppelt, Maren, Owens & Rall (1963); Pollay & Davson (1963). The present studies were designed to investigate certain aspects of this relation, not as it applies to CSF as a whole, but with respect specifically to the fluid formed by the choroid plexus of the lateral ventricle. The effect on the volume and composition of newly formed choroid-plexus fluid was determined when PCo, was altered in the plasma, when Pco2 was altered on the CSF side of the choroid-plexus membrane, and when a carbonic anhydrase inhibitor, acetazolamide, was applied topically to the choroid plexus.In addition, a study was made of the effect on choroid-plexus fluid of the cardiac glycoside, ouabain, applied topically. METHODSThe operative procedure and the methods used to sample and analyse the plasma and choroid-plexus fluid have been described in the preceding paper (Ames, Higashi & Nesbett, 1965).In general pattern, the experimental procedure involved sampling of arterial plasma and choroid-plexus fluid under control conditions; introduction of the experimental variable; sampling again after 30 and (usually) 60 min under the test situation. In some instances, conditions were again returned to the control situation and samples taken 30 min later. Residual choroid-plexus fluid was evacuated and discarded before beginning each collection.The cats were maintained on artificial respiration throughout these studies. An effort was made to adjust the stroke volume and rate of the respiration pump to maintain normal arterial pH under control conditions, though in fact it averaged somewhat above normal at about 7-5. To lower plasma PCO2 the animals were hyperventilated by doubling the stroke volume of the respiration pump and tripling the rate, still using room air. To increase plasma PCO2, a mixture of 10 % CO2 and air was substituted for air without changing the rate or stroke volume of the respiration pump; for this study, most of the animals were curarized.The PCO2 on the CSF side of the choroid plexus was varied by bathing the plexus alternatively in Pantopaque pre-equilibrated with 5 % CO2 in air or in Pantopaque pre-equilibrated simply * Present address: Yamaguchi Medical School, Ube, Yamaguchi Prefecture, Japan.

“…Additional injections of Nembutal, 6 or 12 mg, were given as necessary. Bilateral ventricular-cisternal perfusion was performed according to the method of Pollay & Davson (1963), as modified by Oldendorf & Davson (1967). The artificial c.s.f.…”

Section: Methodsmentioning

confidence: 99%

Efflux mechanism contributing to the stability of the potassium concentration in cerebrospinal fluid

Bradbury¹,

Štulcová²

1970

120

SUIMMARY1. The clearance of 42K from c.s.f. has been separated into two components by means of ventriculo-cisternal perfusion in the rabbit. At 2 hr the largest fraction of radioactivity is recoverable from brain. A smaller fraction passes into the bloodstream and this loss can be expressed as a barrier clearance.2. The clearance into brain was largely independent of potassium concentrations in the perfusion fluid of 15 m-equiv/l. and below. It was depressed by ouabain, 10-2 mM.3. The barrier clearance was small, about 9 % of the total, when the perfusion fluid contained potassium (1.5 m-equiv/l. or below). Above this concentration it increased steeply reaching 32 ,ul./min or 37 % of the total at 10 m-equiv/l. A similar high barrier clearance was caused by replacing 84 % of the sodium in the perfusion fluid with choline.