= ON retinal bipolar cell
{c}
= Retinal ON-bipolar cell
{synonym}
An <ON retinal bipolar cell> is a <retinal bipolar cell> whose central receptive response shows <depolarization> when illumination increases appropriately. At the input <synapse>, this reverses the response sign of a <photoreceptor>, which undergoes <hyperpolarization> in response to <light> and releases less <glutamate>.<TRPM1 is required for the depolarizing light response in retinal ON-bipolar cells by Catherine W. Morgans and others>[Introduction; photoreceptor and ON-bipolar response polarity]{ref}
The postsynaptic <glutamate>-sensing receptor <mGluR6> controls a current requiring <TRPM1>. In a 2009 study, <TRPM1>-deficient mice retained the rod-related electroretinogram a-wave but lacked the b-wave; direct recordings of bipolar responses provided evidence for a postsynaptic signaling defect.<TRPM1 is required for the depolarizing light response in retinal ON-bipolar cells by Catherine W. Morgans and others>[Abstract and Figures3–4; ERG and direct recordings]{ref}
A local sign model makes the circuit transformation visible. If a small light increment $\delta L$ changes glutamate release by $\delta G=-a\delta L$ and the ON response obeys $\delta V=-b\delta G$, with $a,b>0$, then $\delta V=ab\delta L>0$. These are illustrative gains, not fitted measurements. The label describes response polarity under specified stimulation, not continuous firing or identical behaviour in every ON subtype.
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