ANALYTICAL SCIENCES 2001, VOL.17 SUPPLEMENT i1531 2001 © The Japan Society for Analytical Chemistry New Method to Analyze the Electrophysiological Pathway in the Mouse Brain Toshiyuki HOSOKAWA, 1† Masaaki KURASAKI, 2 and Takeshi SAITO 3 1† Research Division for Higher Education, Center for R&D in Higher Education, Hokkaido University, Sapporo 060-0817, Japan (E-mail: thoso@high.hokudai.ac.jp) 2 Department of Environmental Medicine and Informatics, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan 3 Laboratory of Environmental Biology, Hokkaido University School of Medicine, Sapporo 060-8683, Japan The high-speed camera has become to be able to take sequential two-dimensional images with 0.6 msec per one frame. The images of voltage change in the mouse hippocampal slice were recorded with high-speed camera system (Deltaron; Fujifilm, Tokyo, Japan) and data processing was executed with homemade software. It shows the electrophysiological pathway in the mouse brain using voltage sensitive dye. However the images include so many points (128 x128) and it was difficult to image the actual signal transmission with such huge data. We developed new analysis method that shows the pathway with only two pictures. One picture shows the maximum value of each point and shows the distribution of signals in the slice. The other shows the time when the maximum value was recorded at each point and shows the time with colors. Each color shows the time point of the maximum value was recorded. This picture shows the actual signal transmission at a glance. Moreover it suggests a hardware which can take signal transmission hundreds times faster than the ordinary CCD camera. (Received on August 10, 2001; Accepted on September 13, 2001) Neuronal plasticity, including long-term potentiation (LTP), has been studied for long period. In the case of LTP, high-frequency stimuli to the excitatory monosynaptic pathway cause a continuous increase in the efficiency of synaptic transmission. It was first described by Bliss and Lømo in 1973 1 and has also been reported that it is induced in many excitatory synapses in other parts of the brain 2 . From these studies, LTP has been the dominant model for activity-dependent synaptic plasticity in the mammalian brain 2 . Observation on these kinds of phenomena has possibility to understand the neural network system of the brain. Recording at multiple points was required for this purpose. However, until recently, a few recording electrodes were the only method to record the electrophysiological system in brain slices to observe the neural network. Spatio-temporal patterns of neuronal activity were recorded before and/or after the induction of LTP with a few potentials of recording sites. To increase the number of recording site, an optical recording technique using a high-speed CCD camera with thousands of CCD cells and voltage sensitive dye has been employed in this research area. Recently, Iijima et al. 3 developed a fast metal-oxide semiconductor (MOS) photo detector which had high spatial resolution (128x128 pixels), high time (1 frame per 0.6 msec) resolution and high voltage resolution (16 bit in pseudo calculation). However the raw data is difficult to manage because they include too many two dimensional images like Fig. 3. In this study, we introduced a new method to show continuous two-dimensional images in several figures. This method makes us easy to understand the temporal pattern by a glance. Moreover it shows that this method can be utilized as a hardware and it makes the data processing speed hundreds times faster than the ordinary CCD camera. Experimental Electrophysiological and Optical Recording Four- to six-week-old male ddY mice (Hokudo, Sapporo. Japan) were used for the experiment. Mice were decapitated under ether anesthesia and transverse hippocampal slices were cut 300 μm thick using a vibroslicer. The slices were stored for at least 1 h in a storage chamber filled with artificial cerebrospinal fluid (ACSF) containing 120 mM NaCl, 3 mM KCI, 23 mM NaHCO 3 , 1.2 mM NaH 2 PO 4 , 11 mM glucose, 2.4 mM CaCl 2 , and 1.2 mM MgSO 4 , bubbled with a 95% O 2 and 5% CO 2 gas mixture. The slices were transferred to a merged recording chamber placed on the stage of an inverted microscope (TMD-300; Nikon) and continuously perfused with ACSF at a rate of 2-3 ml/min at room temperature. Test electrical stimulation (up to 40 V, constant voltage, 50 μsec duration) at a rate of 0.033 Hz was applied to stimulate Schaffer collaterals through a tungsten electrode (0.005" 5 Mohm; A-M systems Inc., WA, USA) placed at the stratum radiatum of subfield Cornu Ammonis 1 (CA1). Response to test stimuli was recorded through a glass extracellular electrode (filled with 2M KCl and 5% brilliant blue) placed at the stratum pyramidale of CA1 (Fig.1). Then it was amplified (MEG- 1251; Nihon Koden, Tokyo, Japan), digitized with an AD-DA converter (ITC-16; InstruTech, NY, USA) and stored in the hard drive of a personal