Multiunit recording of cortico-hippocampal system of rats

Abstract

Event Abstract Back to Event Multiunit recording of cortico-hippocampal system of rats Ana Kunicki1*, Edgard Morya2, 3, Miguel Nicolelis2, 4, 5, Sidarta Ribeiro2, 5 and Koichi Sameshima1, 2, 3 1 University of São Paulo Medical School, Brazil 2 Alberto Santos Dumont Research Support Association, Department of Neuroscience, Faculty of Health,Medicine and Life Sciences, Brazil 3 Sírio Libanês Hospital, Teaching and Research Institute, Brazil 4 Duke University Medical Center, Center for Neuroengineering, United States 5 Edmond and Lily Safra International Institute of Neuroscience of Natal, Department of Neuroscience, Faculty of Health,Medicine and Life Sciences, Brazil The cortico-hippocampal system has an important role in memory consolidation. We have constructed microelectrodes array to study the dynamics of interaction among cerebral regions. The electrodes array consists of 32 teflon coated tungsten sharp microwires (diameter 50 μm; impedance 1-3 MΩ at 1 kHz measured in saline). Each array was built with specific stereotaxic coordinates to implant in the hippocampus (2.4 - 3.8 mm caudal to bregma; 1.0 - 3.0 mm lateral to bregma e 2.0 mm depth for layer CA1) and prefrontal cortex(0.5 - 4.2 mm rostral to bregma; 0.4 – 1.0 mm lateral to bregma and 1.6 mm depth for layer III-V)1. Each electrode was spaced 320 μm in the antero-posterior and 300 μm in the medio-lateral axis. The electrodes array was fixed with epoxy paste, soldered in a printed circuit board and connected to miniature connector (Omnetics, MN, USA)2. The arrays were implanted in male Wistar rats (n=4) at the right hemisphere, in accordance with NIH guidelines for survival surgery. Rats were anesthetized with Ketamine (100 mg/kg) and Xylazine (5 mg/kg) following induction with Halothane. One week after surgery, single-unit and multi-unit activities were recorded (Plexon Inc, TX) in the freely moving rat, two hours a day, during one month. After euthanasia and perfusion, 50 μm frozen sections were cut and stained with Nissl coloration to identify the electrodes position. We have recorded in average (±SD) 41±9 neurons in the hippocampus and 53±13 neurons in the prefrontal regions based on the quantification of multiple parameters (waveform voltage and shape, and interspike interval). These data recorded chronically of neuronal populations simultaneously allow understanding the dynamic of cortico-hyppocampal system, that is essential for the comprehension of the neural mechanisms underlying memory consolidation. Financial Support: Alberto Santos Dumont Research Support Association (AASDAP); The State of São Paulo Research Foundation (FAPESP); Coordination for the Improvement of Higher Education Personnel (CAPES); Sírio Libanês Hospital; Counsel of Technological and Scientific Development (CNPq); Duke University and The Brazilian Innovation Agency (FINEP).