A STUDY OF CENTRAL NERVOUS SYSTEM BARRIERS USING TRITIATED BARBITAL
Abstract
Randomly labeled tritiated barbital was used in this investigation to study the ability of physostigmine, acetazolamide and methazolamide to facilitate barbital penetration from the cerebrospinal fluid into the brain. The study was prompted by the reports (Greig, M.E. and T.C. Mayberry, J. Pharmacol. Exptl. Therap., 102, 1 (1951); Kerley, T.L., Ph.D. Thesis, Purdue University, 1958) that two of these agents alter blood-brain barrier permeability to barbital.The tritiated compound was purified prior to use. Labile tritium was removed by repeated equilibration with water. Impurities were removed by recrystallization to constant specific activity from ethanol-water and toluene solvents followed by liquid-liquid column partition chromatography. Purity of the product was shown by the presence of a single radioactive spot after paper chromatography and by regression analysis of variance (Baggett, B. and L.L. Engel, J. Biol. Chem., 229, 443 (1957)). Initial specific activity of 282 mc/g was reduced to approximately 252 mc/g in the purification steps. An insignificant loss of activity was found for barbital-t isolated from the serum of a rabbit.Acetazolamide, methazolamide and physostigmine were tested for their ability to alter barbital penetration from cerebrospinal fluid into brain. The modifiar" drugs were administered to rata minutes prior to injection of tritiated barbital (8 pc) Intracisternally. The animals were sacrificed 5 minutes after barbital-t injection and brain and blood levels were determined. The drug treated and control groups were as follows:A No Drug Control: Saline, 0.5, intraperitoneallyAcetazolamide: 200 mg/ke, subcutaneouslyC. Kethanolamide: 100 mg/kg, subcutaneouslyD. Drug Control: CL-13,8501 100 mg/kg, subcutaneously5. Physostigmine Salicylate: 0.8 ng/kg, intraperitoneallyA randomized block experimental design was used.orbital brain and blood level dats were subjected to the analysia of variance.No significant difference in brain or blood barbital-t levels was observed between control and "modifier" pretreated animals. Cholinesterase inhibition by physostigmine and carbonic anhydrase inhibition by acetazolamide and nothazolemide apparently were not effective in facilitating barbital penetration into brain from cerebrospinal fluid. The results with physostigmine were surprising in view of the report by Greig and Carter (Arch. Biochem. Biophys., 52, 175 (1954)) that physostigmine enhanced barbital penetration into brain alices in vitro. If acetanolantde acted to alter blood-brain barrier permeability in the study by Kerley (Ph.D. Thesis, Purdue University, 1358) by an alteration in blood pff the affects of the carbonic anhydrase inhibitors in this study would not have been expected, since serebrospinal fluid p is altered little by the drugs 18118, L., C.H. Carter and T.H. Naren, J. Pharmacol. Exptl. Therap., 122, 6A (1955)). If a change within the brain tissue was responsible for the blood-brain barrier alteration observed by Herloy, then the action of all three modifiera employed in this study may have been masked by the pial membrane.
Degree
Ph.D.
Subject Area
Pharmacology
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.