The retina divides visual information into ON- and OFF signals, and processes each signal with independent subsets of neurons in parallel. So far no difference between the ON pathway and the OFF pathway has been found for neurotransmitter functions. We have previously reported that the immunoreactivity for P2X2-purinoceptors of cholinergic amacrine cells is OFF-pathway-specific in the mouse retina. We therefore examined if ATP has different functions between the ON pathway and the OFF pathway using the patch clamp technique and the multi-electrode recording system. Only the OFF-type, but not the ON-type, cholinergic amacrine cells responded to ATP vigorously. This response was mediated by the P2X2-purinoceptors. Furthermore, PPADS, a P2X-purinergic receptor antagonist, activated the tonic phase firing of the OFF-type ganglion cells, but not of the ON-type ganglion cells. Thus P2X-purinergic receptors selectively modulate OFF-pathway in the mouse retina. [J Physiol Sci. 2007;57 Suppl:S11]
