Glycine- and GABA-activated inhibitory currents on axon terminals of rabbit cone bipolar cells
Glycine- and GABA-activated currents were examined in the axon terminals of 12 types of rabbit cone bipolar cells. In the superfused retinal slice, a cell was voltage clamped at 0 mV in the presence of cobalt; then glycine or GABA was puffed onto the axon terminal. Types CBa1, CBa2, and a few CBa1-2 cells demonstrated larger glycine-activated currents than GABA-activated ones. However, some OFF cells (CBa2n, CBa1-2n, CBa1w), most CBa1-2, and most ON cells (CBb3, CBb3-4, CBb3n, and CBb4) displayed larger GABA-activated currents. The ON cell, CBb5, possessed only a GABA-activated current. The predominance of glycinergic currents in CBa1, CBa2, and a few CBa1-2 cells suggests a major input from the glycinergic AII amacrine cell and thus a key role for these cells in the rod bipolar pathway. Certain OFF cells (most CBa1-2) expressed larger GABA-activated currents. All types expressed both GABAA and GABAC currents about equally, although most OFF types (CBa1, CB a2n, CBa1-2, and CBa2n) displayed a slightly greater GABAA component.(Received March 24 2005)
(Accepted May 24 2005)
Key Words: Glycine-activated current; GABA-activated current; ON and OFF cone bipolar cell; Axon terminals.
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