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Cone bipolar cells and cone synapses in the primate retina

Published online by Cambridge University Press:  02 June 2009

B. B. Boycott
Affiliation:
Department of Anatomy, United Medical and Dental Schools of Guy's and St. Thomas's Hospitals (Guy's Campus), London Se1 9Rt, UK
J. M. Hopkins
Affiliation:
Department of Anatomy, United Medical and Dental Schools of Guy's and St. Thomas's Hospitals (Guy's Campus), London Se1 9Rt, UK

Abstract

Primate retinal bipolar cells synapsing with two adjacent cones (2C bipolars) are further described. Their synaptic contacts are either as the central (invaginating) component of the cone triads or as basal (flat) contacts on the membrane of the cone pedicle base. Correspondingly, their axons end either in the b (inner) half or in the a (outer) half of the inner plexiform layer. The shape and size of the axon terminals of 2C bipolars are indistinguishable from those of adjacent midget bipolars. Therefore 2C bipolars, like midget bipolars, probably synapse with midget ganglion cells. Two C bipolars have not been identified as connected to foveal cones. But they are not restricted to the retinal periphery, as has previously been supposed, since they occur, mixed with midget (single cone) bipolars, throughout all parts of the retina from about 2.5 mm to atleast 10.0 mm from the fovea. It is likely that 2C bipolars are a variant of the midget bipolars; and that they contact some members of the same population of cones, instead of the midgets. This paper briefly reviews, and raises some new, problems concerning our current understanding of the synaptic connectivity patterns of the midget, 2C, and diffuse cone bipolar cells.

Information

Type
Research Articles
Copyright
Copyright © Cambridge University Press 1991

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