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Signal transmission in the catfish retina. I. Transmission in the outer retina.

Extrinsic current, either pulsatile or white-noise modulated, was injected into the (cone) horizontal-cell soma and axon, and resulting responses were recorded from nearby points. In the case of white-noise inputs, signal transmission between the two points was characterized by Wiener kernels. The signal transmission within the lamina, the S-space, formed by the (cone) horizontal-cell somas and axons is quasi-linear and very fast, indicating that the laminae are purely resistive networks within the frequency range of the light-evoked response. There exists signal transaction between the lamina formed by the somas and axons. The forward transmission is constant gain, low pass, but there is a filter for the reverse transmission to impede the backflow of high-frequency components. Signals in the horizontal-cell soma are transmitted to the bipolar cells. The transmission is sign noninverting for the on-center bipolar cells and sign inverting for the offcenter cells. The transmission is quasi-linear excluding complex mechanisms in the transmission. We believe that the forward and direct transmission of signals from the horizontal to bipolar cells is the most straightforward interpretation of the observation. The transfer functions between the horizontal and bipolar cells differ considerably from one bipolar cell to the next.

Animals↗

[Transplantation of neural retina after photic injury of retina in mice].

OBJECTIVE: To examine the possibility of retinal photoreceptors rescued after photic injury by allogeneic neural retinal transplantation. METHODS: The retinal photic injury model was established by a light-damage trunk designed by ourselves. After photo-illumination, 60 mice were divided into two groups: Group I (n = 20) was the photic injury group and group II (n = 40), the retinal transplantation group; then group II was subdivided into II(A) (n = 20) and II(B) (n = 20) subgroups. External approach for neural retinal transplantation was performed at 24hr (group II(A)) and day 7 (group II(B)) after photic injury respectively. The recipients were sacrificed at day 6, day 12, day 18 and day 30 post-operatively to examine whether the graft could rescue the injured retinal photoreceptors. RESULTS: In group I, the inner and outer segment showed edema, disorganization and vesiculation, the outer nuclear layer became very thin and disorganized, and the cell nuclear chromatin showed pyknosis and margination. In group II, the graft survival rate in group II(A) was 50% (10/20) and in group II(B) was 80% (16/20), the difference being significant (chi(2) = 3.956, P < 0.05). Among the graft survival samples, we compared the rescue rate of photoreceptors between group II(A) 40% (4/10) and group II(B) 50% (8/16), the difference being not significant (P = 0.702). CONCLUSION: The retinal photic injury may result in photoreceptor degeneration that can be rescued by retinal transplantation, and the successful rate of the transplantation performed at day 7 is higher than that at 24-hr after injury.

Animals↗