Research in Dr. Pittler’s laboratory focuses on the biochemistry and molecular biology of photoreceptor cells. Within these cells, the initial events mediating vision occur. Light is absorbed in the photoreceptors by the receptor molecule rhodopsin, which then activates another protein, transducin. Transducin activates a third protein, cGMP phosphodiesterase (PDE), that leads to the hydrolysis of cyclic guanosine monophosphate (cGMP). The drop in cGMP levels closes a cGMP-gated cation channel in the plasma membrane, triggering the formation of an electrical impulse that is transmitted to the brain. Guanylate cyclase mediates the return to the dark state by replenishing the cGMP levels. Other ancillary proteins regulate the system to allow a response over eight orders of magnitude of light intensity.