title: Monitoring of met-enkephalin in vivo with 5-min temporal resolution using microdialysis sampling and capillary liquid chromatography with electrochemical detection.
abstract: A method based on microdialysis sampling and capillary liquid chromatography with electrochemical detection that allows in vivo monitoring of met-enkephalin with 5-min temporal resolution is described. Sampling was achieved using a concentric microdialysis probe made from polycarbonate membrane material with a 20 kDa cut-off. This probe had an in vitro relative recovery for met-enkephalin of 63% at a dialysis flow-rate of 0.6 microl/min. Separations were performed using 7 cm x 25 microm I.D. fused-silica capillary columns packed with 5 microm Alltima C18 particles. A carbon fiber microelectrode was used as the detector electrode. The mass detection limit for met-enkephalin with this system was 40 amol. With on-column preconcentration, up to 2 microl of sample could be loaded onto the column resulting in concentration detection limits as low as 20 pM for met-enkephalin. Direct injection of dialysate, collected at 5-min intervals, allowed determination of met-enkephalin concentrations in the rat globus pallidus under basal and K+-induced depolarization conditions.
authors.affiliation: Department of Chemistry, University of Florida, Gainesville 32611-7200, USA.
authors.forename: H
authors.initials: H
authors.lastname: Shen
authors.forename: M W
authors.initials: MW
authors.lastname: Lada
authors.forename: R T
authors.initials: RT
authors.lastname: Kennedy
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004563:Electrochemistry; D004744:Enkephalin, Methionine / Q000032:analysis* / Q000378:metabolism; D005917:Globus Pallidus / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D004744:Enkephalin, Methionine; D011188:Potassium