blocking retinal chloride co-transporters kcc2 and nkcc impact on direction selective on and off responses in the rat’s nucleus of the optic tract阻断视网膜氯co-transporters kcc2和nkcc影响方向选择性,反应大鼠视神经束的细胞核.pdfVIP

Blocking Retinal Chloride Co-Transporters KCC2 and NKCC: Impact on Direction Selective ON and OFF Responses in the Rat’s Nucleus of the Optic Tract 1 1 1 2 Katharina Spoida , Claudia Distler , Anne-Kathrin Trampe , Klaus-Peter Hoffmann * ¨ ¨ 1 Allgemeine Zoologie and Neurobiologie, Ruhr-Universitat Bochum, Bochum, Germany, 2 Tierphysiologie, Ruhr-Universitat Bochum, Bochum, Germany Abstract In the present study we investigated in vivo the effects of pharmacological manipulation of retinal processing on the response properties of direction selective retinal slip cells in the nucleus of the optic tract and dorsal terminal nucleus (NOT- DTN), the key visuomotor interface in the pathway underlying the optokinetic reflex. Employing a moving visual stimulus consisting of either a large dark or light edge we could differentiate direction selective ON and OFF responses in retinal slip cells. To disclose the origin of the retinal slip cells’ unexpected OFF response we selectively blocked the retinal ON channels and inactivated the visual cortex by cooling. Cortical cooling had no effect on the direction selectivity of the ON or the OFF response in NOT-DTN retinal slip cells. Blockade of the retinal ON channel with APB led to a loss of the ON and, to a lesser degree, of the OFF response and a reduction in direction selectivity. Subsequent blocking of GABA receptors in the retina with picrotoxin unmasked a vigorous albeit direction unselective OFF response in the NOT-DTN. Disturbing the retinal chloride homeostasis by intraocular injections of bumetanide or furosemide led to a loss of direction selectivity in both the NOT-DT