Variations in structure and response properties of horizontal cells in the retina of the rabbit.

The response waveform of rabbit horizontal cells to diffuse white light stimulation was correlated with their anatomy by intracellular injection of horseradish peroxidase. In both axonless horizontal cells and the somatic end of axon-bearing cells the light evoked hyperpolarization may exhibit a transient at the onset of high intensity stimuli and is consistently followed by a rod aftereffect at stimulus cessation. In both types of cells the on-transient may be small and the rod aftereffect very prominent; this response pattern, however, is more frequently a property of the somatic end of axon-bearing cells. The morphology of axon-bearing cells is the same regardless of their response properties. On the other hand, axonless horizontal cells exhibit a wide variation in shape and the vast majority of them have asymmetric dendritic fields. No correlation, however, exists between cell shape and response properties. These are also independent of the location of horizontal cells in the retina or the orientation of their long axis with respect to the optic nerve head and medullary rays.