Akimichi Kaneko

Physiological and morphological identification of horizontal, bipolar and amacrine cells in goldfish retina

1. Intracellular recordings were made from various types of cells in the isolated goldfish retina, and Procion Yellow was injected from the recording pipette in order to identify histologically the structure recorded. The dye diffused and stained the cell body and processes down to the fine branches.

Electrical connexions between horizontal cells in the dogfish retina

1. In dogfish, studies were made of electrical connexions between pairs of cells giving S‐potentials. After recording, the types and locations of the two cells were determined morphologically by electrophoretically injecting two different fluorescent dyes.

Spectral response curves of single cones in the carp

Abstract Single cone spectral response curves were obtained with the aid of specially designed equipment. Statistical analysis of 142 records selected from hundreds, based solely on the greatest signal-to-noise ratio, revealed three groups of cones; the red cones (74 per cent) with the peaking wavelength at 611±23mμ, green cones (10 per cent) at 529±14mμ , and blue cones (16 per cent at 462±15mμ). These peaking wavelengths are in close accord with those of single cone absorption spectra measured by Marks and MacNichol in the goldfish by a microspectrophotometer. Apparently, Youngs trichromatic theory applies at the photoreceptor level in Cyprinidae.

Receptive field organization of bipolar and amacrine cells in the goldfish retina

1. Intracellular recordings were made from bipolar and amacrine cells in the isolated goldfish retina. Cells were identified mainly from their response patterns to a spot and an annulus in reference to the knowledge obtained from the previous work of intracellular Procion Yellow injection. Using white light and monochromatic lights receptive field organization of recorded cells were analysed.

pH Changes in the Invaginating Synaptic Cleft Mediate Feedback from Horizontal Cells to Cone Photoreceptors by Modulating Ca2+ Channels

Feedback from horizontal cells (HCs) to cone photoreceptors plays a key role in the center-surround–receptive field organization of retinal neurons. Recordings from cone photoreceptors in newt retinal slices were obtained by the whole-cell patch-clamp technique, using a superfusate containing a GABA antagonist (100 μM picrotoxin). Surround illumination of the receptive field increased the voltage-dependent calcium current (ICa) in the cones, and shifted the activation voltage of ICa to negative voltages. External alkalinization also increased cone ICa and shifted its activation voltage toward negative voltages. Enrichment of the pH buffering capacity of the extracellular solution increased cone ICa, and blocked any additional increase in cone ICa by surround illumination. Hyperpolarization of the HCs by a glutamate receptor antagonist-augmented cone ICa, whereas depolarization of the HCs by kainate suppressed cone ICa. From these results, we propose the hypothesis that pH changes in the synaptic clefts, which are intimately related to the membrane voltage of the HCs, mediate the feedback from the HCs to cone photoreceptors. The feedback mediated by pH changes in the synaptic cleft may serve as an additional mechanism for the center-surround organization of the receptive field in the outer retina.

Electrophysiological study of single neurons in the inner nuclear layer of the carp retina

Abstract Intracellular recording was made from cells in the inner nuclear layer of the carp retina. Judging from the depth measurement, from electrode marking studies and from the lack of responsiveness to direct stimulation of the optic nerve, they were considered to be bipolar cells and amacrine cells. The responses consisted of slow potentials and sometimes of spikes. The response types were classified into three groups: “on,” “off” and “on-off”. Among the “on” and “off” type units, some had a concentric receptive field consisting of an on-center off-periphery or vice versa, while other units had a uniform receptive field. The “on-off” type was fixed to any stimulus patterns. The size of the receptive field, more than several millimeters in many cases, was larger than the dendritic field of bipolar cells or amacrine cells. The latency of the responses was longer than that of the

Adrenaline enhances odorant contrast by modulating signal encoding in olfactory receptor cells

Olfactory perception is influenced by hormones. Here we report that adrenaline can directly affect the signal encoding of olfactory receptor cells. Application of adrenaline suppressed action potentials near threshold and increased their frequency in response to strong stimuli, resulting in a narrower dynamic range. Under voltage–clamp conditions, adrenaline enhanced sodium current and reduced T–type calcium current. Because sodium current is the major component of spike generation and T–type calcium current lowers the threshold in olfactory receptor cells, the effects of adrenaline on these currents are consistent with the results obtained under current–clamp conditions. Both effects involved a common cytoplasmic pathway, cAMP–dependent phosphorylation. We suggest that adrenaline may enhance contrast in olfactory perception by this mechanism.

S‐potentials in the dark‐adapted retina of the carp

1. S‐potentials were recorded in the dark‐adapted carp retina. After recording, Procion Yellow was injected from the recording electrode to identify histologically the cell recorded.

Differentiation of PIII subcomponents in cold-blooded vertebrate retinas

Abstract The P III fraction was analysed on isolated inverted retinas obtained from frogs and turtles by means of the coaxial microelectrode. It was found that the conventional P III consisted of at least two subcomponents; the distal P III arising in the receptor cell layer and the proximal P III originating in a more proximal layer. Latency measurements revealed that the onset of the distal P III occured sooner than that of the proximal P III. Furthermore, these two subcomponents differed in resistivity to ammonia vapor. Utilizing the excised opened frog eye, electrode placement between the origins of the distal and proximal P IIIs resulted in a biphasic deflexion prior to the onset of the b-wave. This deflexion was a consequence of differences in latency and polarity between the P III subcomponents.

Recording site of the single cone response determined by an electrode marking technique.

Abstract An electrode marking technique was applied on the single cone response in the carp retina. A dye, Niagara Sky Blue 6B, was injected electrophoretically from the recording micropipette. In order to identify the stained cell, the retinas were prepared histologically and examined under the microscope. The observation that the cone inner segment was stained blue substantiated the intracellular nature of the response. The essential conditions for faithful electrode localization was also discussed.