Push-Pull Model of Dopamine’s Action in the Retina

Abstract

Although our knowledge of the interactive connections in the mammalian retina has greatly expanded over the last 20 years, the exact wiring and functional role of this complex network has not yet been elucidated. Ganglion cells receive input from the vertical pathways (photoreceptors — bipolar cells — ganglion cells) and lateral pathways (photoreceptors — horizontal cells — bipolar cells — amacrine cells) of retinal interneurons (Werblin and Dowling, 1969). Contrary to the ganglion cell responses which can be recorded from the optic nerve, the three classes of retinal interneurons (horizontal, amacrine and bipolar cells) are not easily accessible and recordings are further limited by their small size, especially in higher vertebrates. Together with photoreceptors and the ganglion cells, they make up the complex network of the mammalian retina. Ganglion cells have a characteristic center-surround antagonistic organization in their receptive fields (Kuffler, 1953; Rodieck and Stone, 1966; Enroth-Cugell and Robson, 1966) (Fig. 5.1). It has been shown, however, that bipolar neurons of the primate, which precede ganglion cells in the vertical pathway, also have surrounds (Dacey et al, 2000).