Development of a method of "Voltage Clamp by light" for the study of visual neurons

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The method of voltage clamp has provided physiology with a basic experimental paradigm for mofe than three decades. It is not, however,feasible in some cases, due to problems arising from the cell morphology (size and shape) , electrical connection with other cells, and etc. This is true with many visual neurons, and often one can learn little about important subjects such as synaptic mechanisms to mediate the photo-response. The purpuse of this research was to get around the problem by developing a new voltage clamp method which makes use of the natural stimulus to the visual system. namely light. We feel that the aim has adequately been attained, as is summarized below.1. Development of the Method of " Voltage Clamp by Light "(1.1) Protype System: a servomechanical apparatus was designed and fabrica ted, which automatically controls the light intensity on the basis of membrane voltage error signal.(1.2) Extended System: the bridge-balance method was incorporeted with the preceding prototype, to allow simultaneous measurement of the membrane resistance under the voltage clamp by light.2. Application Research i: the eqipment of (1.1) was used to measure DC and AC spectral sensitivities of horizontal cells in the carp retina. A new observation was made from this result, bearing close relevance to the finding of 3.3. Application Research ii: the system of (1.2) was used to investigate the synaptic mechanisms from cone photoreceptors to horizontal cells. The result necessitates a revision on a popular notion in this field.4. Application Research iii: the apparatus of (1.2) was applied to find a new phenomenon asscociated with the process of light adaptation in the crayfish photoreceptor cell.