title: Rapid assessment of in vivo cholinergic transmission by amperometric detection of changes in extracellular choline levels.
abstract: Conventional microdialysis methods for measuring acetylcholine (ACh) efflux do not provide sufficient temporal resolution to relate cholinergic transmission to individual stimuli or behavioral responses, or sufficient spatial resolution to investigate heterogeneities in such regulation within a brain region. In an effort to overcome these constraints, we investigated a ceramic-based microelectrode array designed to measure amperometrically rapid changes in extracellular choline as a marker for cholinergic transmission in the frontoparietal cortex of anesthetized rats. These microelectrodes exhibited detection limits of 300 nm for choline and selectivity (> 100 : 1) of choline over interferents such as ascorbic acid. Intracortical pressure ejections of choline (20 mm, 66-400 nL) and ACh (10 and 100 mm, 200 nL) dose-dependently increased choline-related signals that were cleared to background levels within 10 s. ACh, but not choline-induced signals, were significantly attenuated by co-ejection of the acetylcholinesterase inhibitor neostigmine (Neo; 100 mm). Pressure ejections of drugs known to increase cortical ACh efflux, potassium (KCl; 70 mm, 66, 200 nL) and scopolamine (Scop; 10 mm, 200 nL), also markedly increased extracellular choline signals, which again were inhibited by Neo. Scop-induced choline signals were also found to be tetrodotoxin-sensitive. Collectively, these findings suggest that drug-induced increases in current measured with these microelectrode arrays reflect the oxidation of choline that is neuronally derived from the release and subsequent hydrolysis of ACh. Choline signals assessed using enzyme-selective microelectrode arrays may represent a rapid, sensitive and spatially discrete measure of cholinergic transmission.
authors.affiliation: Psychobiology and Behavioural Neuroscience, Department of Psychology, Ohio State University, Columbus, OH, USA.
authors.forename: Vinay
authors.initials: V
authors.lastname: Parikh
authors.forename: Francois
authors.initials: F
authors.lastname: Pomerleau
authors.forename: Peter
authors.initials: P
authors.lastname: Huettl
authors.forename: Greg A
authors.initials: GA
authors.lastname: Gerhardt
authors.forename: Martin
authors.initials: M
authors.lastname: Sarter
authors.forename: John P
authors.initials: JP
authors.lastname: Bruno
mesh_terms: D000109:Acetylcholine / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001923:Brain Chemistry; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000737:chemistry / Q000378:metabolism*; D002794:Choline / Q000378:metabolism*; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004563:Electrochemistry / Q000379:methods; D005110:Extracellular Space / Q000378:metabolism*; D008297:Male; D017551:Microdialysis / Q000379:methods; D008839:Microelectrodes; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009388:Neostigmine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D012601:Scopolamine / Q000494:pharmacology; D013268:Stimulation, Chemical; D013997:Time Factors
chemical_list: D002800:Cholinesterase Inhibitors; D018727:Muscarinic Antagonists; D009388:Neostigmine; D011189:Potassium Chloride; D012601:Scopolamine; D002794:Choline; D000109:Acetylcholine