title: Differences in the in vitro and in vivo 5-hydroxytryptamine extraction performance among three common microdialysis membranes.
abstract: The present study summarizes the results of an in vitro and in vivo comparison of the apparent 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid, and 3,4-dihydroxyphenylacetic acid dialysis performance of three types of membrane frequently used in intracerebral microdialysis experiments. The dialysis fiber types examined were a regenerated cellulose Cuprophan (GF), a proprietary polycarbonate ether (CMA), and a polyacrylonitrile/sodium methallylsulfonate copolymer (HOSPAL). The experiments unexpectedly revealed that the HOSPAL membrane-equipped probes displayed clearly aberrant 5-HT diffusion dynamics compared with GF and CMA probes, demonstrable not only in vitro, but also in in vivo experiments. In vitro, the GF and CMA membrane-equipped probes exhibited maximum relative recovery for 5-HT already in the first 20-min sample, whereas the 5-HT recovery of HOSPAL probes increased in a very slow and protracted manner over a period of a little less than 2 h. The GF and CMA probes further displayed an immediate washout of 5-HT when the probes were subsequently transferred to artificial CSF only-containing medium (no 5-HT), whereas approximately 2 h was required to yield near-total extinction of dialysate 5-HT with the standard HOSPAL probes. In vivo, the rat ventral hippocampal dialysate 5-HT output responses to K+ (100 mM) infusion, to Ca2+ omission, and to systemic 8-hydroxy-2-(di-n-propylamino)tetralin injection were all markedly retarded and blunted when HOSPAL instead of GF membrane-equipped probes were used. However, the 5-hydroxyindoleacetic acid and 3,4-dihydroxyphenylacetic acid extraction in vitro and in vivo were comparable using either of the membrane types.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology, University of Göteborg, Sweden.
authors.forename: R
authors.initials: R
authors.lastname: Tao
authors.forename: S
authors.initials: S
authors.lastname: Hjorth
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000032:analysis; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002482:Cellulose / Q000031:analogs & derivatives / Q000737:chemistry; D003956:Dialysis / Q000295:instrumentation* / Q000379:methods; D006624:Hippocampus / Q000737:chemistry*; D006897:Hydroxyindoleacetic Acid / Q000032:analysis; D008297:Male; D008567:Membranes, Artificial; D009994:Osmolar Concentration; D011108:Polymers / Q000737:chemistry; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000032:analysis*
chemical_list: D008567:Membranes, Artificial; D011108:Polymers; D015102:3,4-Dihydroxyphenylacetic Acid; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; C011799:5-hydroxy-2-N,N-dipropylaminotetralin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D002482:Cellulose; C009865:cuprammonium cellulose; D011188:Potassium