| Retinal directional selectivity is a classic example of neurocomputation. We identifiedON-OFF direction-selective ganglion cells (DSGCs) and explored their physiological,morphological, pharmacological properties, as well as tracing the emergence of DScircuitry in the retina of mouse, an important mammalian model animal. The mouseON-OFF DSGCs show transient responses to the onset and termination of a stationaryflashing spot, and strong directional selectivity to a moving rectangle. Application ofvarious pharmacological reagents demonstrated that the ON-OFF DSGCs in themouse retina utilized a similar set of transmitters and receptors to compute motiondirection to their counterpart in the rabbit retina. Voltage clamp recording showed thatmouse ON-OFF DSGCs received a larger inhibitory input when stimulus was movingin the null direction and a larger excitatory input when stimulus was moving in thepreferred direction. Visualization of intracellular infused neurobiotin revealed abistratified dendritic field with recursive dendrites forming loop-like structures,previously identified as RGD2 by morphology. Developmental study in new bornanimals suggested that the mouse ON-OFF DSGCs showed clear DS response asearly as postnatal day 11 (P 11), soon after the emergence of bipolar cell ribbonsynapse, and therefore completion of retinal pathway from photoreceptors to ganglioncells. Overall, the ON-OFF DSGCs in the mouse retina exhibit almost identicalproperties to their counterparts in the rabbit retina, indicating that the neuralmechanisms for computing motion direction are conserved from mouse to rabbit, andprobably also to higher mammals. Results from new born mice suggest that DScircuitry develops prior to the bipolar inputs to gangling cells. This studycharacterized the detailed properties of ON-OFF DSGCs in mouse retina, andprovided fundamental information for further understanding of the structure andmaturation of retinal DS circuitry.
|
PDF Full Text Request