Selective Dysfunction of On- and/or Off-Bipolar Cell in Human Diseases
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In human, cone visual signals in the retina are processed through dual pathways, one involving ON-center bipolar cells (ON-pathway) and the other through OFF-center bipolar cells (the OFF-pathway), while rod visual signal is processed only through the ON-pathway. Little is known about how patients can see when the ON- and/or OFF-pathway is selectively defective. By comparing the monkey’s electroretinogram (ERG) of a blocked ON- or OFF-pathway using glutamate neurotransmitter analogs, we have detected new clinical entities in human where ON- and/or OFF-pathways are blocked in both rod and cone visual pathways. We hypothesized that the complete type of congenital stationary night blindness (CSNB 1) can be a model disease, having a complete dysfunction of only the ON-pathway, while the incomplete type (CSNB 2) has an incomplete dysfunction of both the ON- and OFF-pathways in both rod and cone visual systems. The gene mutation was detected in nyctalopin in CSNB 1, and in L-type calcium channel αl subunit in CSNB 2.