H. Wassle et al., IMMUNOCYTOCHEMICAL CHARACTERIZATION AND SPATIAL-DISTRIBUTION OF MIDGET BIPOLAR CELLS IN THE MACAQUE MONKEY RETINA, Vision research, 34(5), 1994, pp. 561-579
Midget bipolar cells form the first distinct step in the parvocellular
(P-) pathway of the primate visual system, and are the major determin
ant of the receptive field properties of colour selective midget gangl
ion cells. This paper describes the sampling properties of the midget
bipolar cell population and relates this to the processing of chromati
c information in the P-pathway. Immunocytochemical markers were used t
o label midget bipolar cells so that their spatial density could be co
mpared with that of cones and ganglion cells. Sections through macaque
monkey retinae were immunostained with antibodies against cholecystok
inin (CCK), and recoverin. In CCK-labelled sections, in addition to bl
ue cone bipolar cells, numerous thin bipolar cell dendrites, which cou
ld be associated with individual cone pedicles are stained. CCK-immuno
reactive midget bipolar cells are found throughout the retina. A diffe
rent population of midget bipolar cells is revealed in recoverin-label
led sections. Based on a comparison with midget bipolar cells in Golgi
-stained retinae we propose that ON-midget (invaginating) bipolars are
immunoreactive for CCK and confirm that OFF-midget (flat) bipolar cel
ls are immunoreactive for recoverin [Milam, Dacey and Dizhoor (1993) V
isual Neuroscience, 10 1-12]. The density of recoverin labelled midget
bipolars matches the cone density to an eccentricity of about 10 mm;
from there outwards it drops to 60% of the cone density. This suggests
convergence of several cones to individual midget bipolar cells in Pe
ripheral retina; We conclude that midget bipolar cells are present thr
oughout the entire primate retina, and could, in peripheral as well as
in central retina, provide chromatically specific input to the P-path
way.