Regulatory effect of dopamine on spatial properties of horizontal cells in carp retina

Three types of light-induced response (L-, RG-, and YRB -type S-potentials) recorded from isolated retinas of the carp (Cyprinus carpio) were identified by their spectral response and later by morphological localization of the recording sites marked with an intracellular Lucifer Yellow (LY). Horizontal cells in a given layer, generating one of the above response types, are electrically coupled via gap junctions, so that the injected LY normally diffused to several neighboring cells. The spatial property of the three types of responses was examined by enlarging the diameter of a light spot (0.25 to 4.0 mm) and displacing the spot (0.5 mm diameter) along a straight 4-mm line which passed over the recording point at the middle. In normal retinas, the half-decay distance of response amplitude with spot displacement was shorter in the order of L-, RG-, and YRB -type responses, and correspondingly the dye diffusion area was narrower in the same order of cells. Dopamine (DA; 10 to 20 microM), applied to the vitreous fluid beneath the isolated retina, altered the spatial property of all types of responses by increasing the amplitude of responses to central spots and decreasing that of those to distant spots, and it restricted the intracellular LY to single injected cells. In contrast, in retinas from which DA interplexiform cells had been deprived by prior destruction with a neurotoxin, 6-hydroxydopamine, the amplitude of responses became smaller while the half-decay distance was longer by 1.1- to 1.6-fold, depending upon the cell type, and the dye diffusion area in all types of cells became wider by 2-fold as compared to those in normal retinas.(ABSTRACT TRUNCATED AT 250 WORDS)