We have identified a putative cGMP-gated cation conductance in rat ret
inal ganglion cells. Both in situ hybridization and polymerase chain r
eaction amplification detected transcripts in ganglion cells that were
highly homologous to the cGMP-gated cation channel expressed in rod p
hotoreceptors. Whole-cell patch-clamp recordings detected a current st
imulated by cGMP due to activation of nonselective cation channels. Th
is current had a reversal potential near 0 mV, showed some outward rec
tification, and could be blocked by Cd2+. The current could also be ac
tivated by a phosphodiesterase inhibitor and the nitric oxide donors s
odium nitroprusside and S-nitrosocysteine. We propose that nitric oxid
e released from an identified subpopulation of amacrine cells may acti
vate this channel to modulate ganglion cell activity.