Site-selective Electrical Recording from Small Neuronal Circuits using Spray Patterning Method and Mobile Microelectrodes

In the attempt to fully understand the mechanism for the formation and realization of tissue-specific functions of living multicellular systems, a couple of experimental conditions is required; grasping both the whole picture and the state of elements of a multicellular system. From this viewpoint, selecting neuronal circuits as the target, we have developed an electrical recording method from cultured small neuronal circuits by combining a simple micropatterning technique with a extracellular recording method using a mobile microelectrode. The simple micropatterning method enabled formation of thousands of individual small neuronal circuits consist of single to tens of neurons in one common 35-mm culture dish without any microfabrication apparatus by means of spraying of poly-D-lysine solution onto non-adhesive culture surfaces. Those small neuronal circuits, derived from embryonic hippocampus of rats, showed spontaneous synchronous firing after 8 days after cell seeding. Any of these small neuronal circuits were accessible with a mobile microelectrode, and their spontaneous firings were recorded noninvasively with single-cell-resolution by positioning the tip on constituent neurons. This set of methods does not require any specialized microfabrication apparatus or chemicals, and has a possibility to be used as a practical recording method of electrophysiological activities of a variety of multicellular organisms