Rutherford EC, Pomerleau F, Huettl P, Strömberg I, and Gerhardt GA
Subjects
Animals, Central Nervous System chemistry, Electrodes, Implanted standards, Electrophysiology instrumentation, Extracellular Fluid chemistry, Extracellular Fluid metabolism, Glutamic Acid analysis, Male, Motor Activity physiology, Neurochemistry instrumentation, Neurons chemistry, Neurons metabolism, Oxidoreductases chemistry, Rats, Rats, Inbred F344, Rats, Long-Evans, Stress, Physiological metabolism, Stress, Physiological physiopathology, Time Factors, Wakefulness physiology, Central Nervous System metabolism, Electrophysiology methods, Glutamic Acid metabolism, Neurochemistry methods
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.