Glycinergic input of small-field amacrine cells in the retinas of wildtype and glycine receptor deficient mice

Amacrine cells are known to express strychnine-sensitive glycine receptors (GlyRs), however, it is not known which of the four GlyR alpha subunits (alpha 1-4) are expressed in this diverse group of cells. Herein, we studied the presence of glycine activated currents and spontaneous inhibitory postsynaptic currents (sIPSCs) of amacrine cells in the mouse retina. By recording glycinergic currents in retinal slices of wildtype mice and of mice deficient in GlyR alpha subunits (Glra1(spd-ot), Glra2(-/-), Glra3(-/-)), we could classify AII and narrow-field amacrine cells (NF, Types 5, 6, 7) on the basis of their alpha-subunit composition. Glycinergic sIPSCs of All cells displayed medium fast kinetics (mean decay time constant tau= 11 +/- 2 ins), which were completely absent in the Glra3(-/-) mouse, indicating that synaptic GlyRs of AII cells mainly contain the alpha 3 subunit. Glycinergic sIPSCs of NF cells had slow kinetics (tau=27 +/- 6.8 ms) that were significantly prolonged in G1ra2(-/-) mice (tau=69 +/- 16 ms). These data show that morphologically distinct amacrine cells express different sets of GlyRs. (C) 2007 Elsevier Inc. All rights reserved.