title: Chronic second-by-second measures of L-glutamate in the central nervous system of freely moving rats.
abstract: l-glutamate (Glu) is the main excitatory neurotransmitter in the central nervous system (CNS) and is associated with motor behavior and sensory perception. While microdialysis methods have been used to record tonic levels of Glu, little is known about the more rapid changes in Glu signals that may be observed in awake rats. We have reported acute recording methods using enzyme-based microelectrode arrays (MEA) with fast response time and low detection levels of Glu in anesthetized animals with minimal interference. The current paper concerns modification of the MEA design to allow for reliable measures in the brain of conscious rats. In this study, we characterized the effects of chronic implantation of the MEA into the brains of rats. We were capable of measuring Glu levels for 7 days without loss of sensitivity. We performed studies of tail-pinch induced stress, which caused a robust biphasic increase in Glu. Histological data show chronic implantation of the MEAs caused minimal injury to the CNS. Taken together, our data show that chronic recordings of tonic and phasic Glu can be carried out in awake rats for up to 17 days in vivo allowing longer term studies of Glu regulation in behaving rats.
authors.affiliation: Anatomy and Neurobiology, Morris K. Udall Parkinson's Disease Research Center of Excellence, Center for Sensor Technology, University of Kentucky, College of Medicine, Lexington, Kentucky 40536-0098, USA.
authors.forename: Erin C
authors.initials: EC
authors.lastname: Rutherford
authors.forename: Francois
authors.initials: F
authors.lastname: Pomerleau
authors.forename: Peter
authors.initials: P
authors.lastname: Huettl
authors.forename: Ingrid
authors.initials: I
authors.lastname: Strömberg
authors.forename: Greg A
authors.initials: GA
authors.lastname: Gerhardt
mesh_terms: D000818:Animals; D002490:Central Nervous System / Q000737:chemistry / Q000378:metabolism*; D004567:Electrodes, Implanted / Q000592:standards; D004594:Electrophysiology / Q000295:instrumentation / Q000379:methods*; D045604:Extracellular Fluid / Q000737:chemistry / Q000378:metabolism; D018698:Glutamic Acid / Q000032:analysis / Q000378:metabolism*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009448:Neurochemistry / Q000295:instrumentation / Q000379:methods*; D009474:Neurons / Q000737:chemistry / Q000378:metabolism; D010088:Oxidoreductases / Q000737:chemistry; D051381:Rats; D011916:Rats, Inbred F344; D020318:Rats, Long-Evans; D013312:Stress, Physiological / Q000378:metabolism / Q000503:physiopathology; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology
chemical_list: D018698:Glutamic Acid; D010088:Oxidoreductases