C-type horizontal cell responses to annular stimuli.

Intracellular recordings of C-type horizontal cells were made in the isolated carp (Cyprinus carpio) retina. The C-type cells were subdivided into two types in accordance with their spectral responses: biphasic (RG) and triphasic (YRB). The responses of the two types of cell were investigated to large fields of centered and annular stimuli with a given wavelength and increasing intensities combination. The threshold and the properties to both centered and annular flashes were different from one another for each hyperpolarizing and depolarizing component of the two types of cells. The hyperpolarizing component at peaks of spectral response curves of the RG- and YRB-cell evoked to the centered flashes always surpassed that evoked to the annular flashes at any intensities. On the other hand, the depolarizing component of the RG- and YRB-cell and the second hyperpolarizing component of the YRB-cell evoked to the centered flashes were reversed in polarity as the intensity was increased. The depolarizing and the second hyperpolarizing component of the two types of cells evoked to the annular flashes were progressively developed at increasing intensities, and surpassed that evoked to the centered flashes at a given intensity. The results obtained show that there is a not-well defined color dependent center-surround organization in the receptive field of C-type horizontal cells.