We are investigating the effects of acetylcholine potentiators, agonists and antagonists on the activity of ganglion cells in the mammalian retina. The rabbit retina is used because it is representative of other mammalian retinas, such as cat and primate, and many types of cell can be recorded more frequently in rabbit than other mammals. We will work particularly with physostigmine, which is an anticholinesterase, and therefore an acetylcholine potentiator. We will observe whether physostigmine effects some cell types but not others and whether, in the types that are effected, some aspects of the receptive field are affected but not others.