TRANSMITTER INTERACTIONS AT THE HORIZONTAL CELL LEVEL IN THE RETINA OF A TELEOST FISH (EUGERRES-PLUMIERI)

In the retina of a teleost fish (Eugerres plumieri), the unique action of dopamine (DA) on the spatial properties of horizontal cells was ascertained to be mediated via the D1 receptor (blocked by SCH 23390 and haloperidol). In the retina from which DA had been depleted by intraperitoneal injection of reserpine, L-glutamate or kainate tended to suppress the surround response, while gamma-aminobutyric acid (GABA) tended to attenuate the center response. Hence, these amino acids appear to participate in the spatial properties of horizontal cells, possibly by altering the input membrane resistance. Furthermore, in some DA-depleted retinas the attenuation of the center response caused by GABA persisted even after a brief application of DA. This suggests that a long-lasting depletion of DA may alter the membrane properties of retinal neurons.