title: Use of cassette dosing to enhance the throughput of rat brain microdialysis studies.
abstract: This study was designed to increase the throughput of rat brain microdialysis studies by administration of compounds as a cassette as opposed to discrete study. Eight compounds (carbamazepine, citalopram, desmethylclozapine, diphenhydramine, gabapentin, metoclopramide, naltrexone, and stavudine) were selected and administered as an intravenous bolus dose at 0.5-3.3 mg/kg each followed by an intravenous infusion at 1 mg/kg per hour for 6 hours in rats in a cassette or discrete dosing. The dialysate, plasma, brain, and cerebrospinal fluid were collected and analyzed using liquid chromatography-tandem mass spectrometry. The microdialysis probe recovery was determined by an in vitro gain method. The recovery between the cassette and discrete dosing was similar, with an average of 1.0 ± 0.10-fold difference. The stavudine interstitial fluid (ISF) concentration, as measured by brain microdialysis, was below the low limit of quantitation and was excluded from the analyses. The ratios of ISF concentration to unbound plasma concentration were within 2-fold for six of the remaining seven compounds, with an average of 0.92 ± 0.51-fold difference between the cassette and discrete methods. The ratios of ISF concentration to unbound brain concentration, as measured by the brain homogenate method, were also similar, with a 1.1 ± 0.7-fold difference. In addition, the ratios of ISF to cerebrospinal fluid concentrations were similar, with a 1.5 ± 0.6-fold difference. The results from this study support the use of a cassette dosing approach to enhance the throughput of rat brain microdialysis studies in drug discovery.
authors.affiliation: Genentech, Inc., South San Francisco, California.
authors.forename: Gauri
authors.initials: G
authors.lastname: Deshmukh
authors.affiliation: Genentech, Inc., South San Francisco, California.
authors.forename: Kefeng
authors.initials: K
authors.lastname: Sun
authors.affiliation: Genentech, Inc., South San Francisco, California.
authors.forename: Bianca M
authors.initials: BM
authors.lastname: Liederer
authors.affiliation: Genentech, Inc., South San Francisco, California.
authors.forename: Xiao
authors.initials: X
authors.lastname: Ding
authors.affiliation: Genentech, Inc., South San Francisco, California liu.xingrong@gene.com.
authors.forename: Xingrong
authors.initials: X
authors.lastname: Liu
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000378:metabolism; D001812:Blood-Brain Barrier; D001923:Brain Chemistry / Q000502:physiology*; D057166:High-Throughput Screening Assays / Q000379:methods*; D007262:Infusions, Intravenous; D008297:Male; D017551:Microdialysis / Q000379:methods*; D004364:Pharmaceutical Preparations / Q000008:administration & dosage / Q000134:cerebrospinal fluid / Q000378:metabolism*; D010599:Pharmacokinetics; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001798:Blood Proteins; D004364:Pharmaceutical Preparations