Acetylcholine (ACh) is synthesized in the retina by two populations of amacrine cells. The effects of ACh are mediated by muscarinic (mAChR) and nicotinic acetylcholine receptors (nAChRs). The three Β and nine a nAChR subunits and 5 mAChR subtypes identified in the vertebrate retina display distinctive physiological and pharmacological characteristics. Amacrine and ganglion cells in the retina express one or more AChR subtypes and there is evidence for expression by subpopulations of bipolar cells as well. ACh can affect the response properties of ganglion cells through receptors expressed by the ganglion cells themselves as well receptors on upstream cells.