Steady state feedback in mammalian phototransduction illustrated by a nomogram.
Published data characterizing the four reactions responsible for the Ca(2+)-mediated negative feedback in mammalian rod phototransduction were used to generate graphs which are combined in a circular fashion so that the y-axis of one serves as the x-axis of the next. The nomogram thus created makes it possible to determine by inspection the steady state situation in darkness, and the quasi-steady state situations that pertain shortly after exposure to light of different intensities. The results predicted by the nomogram suggest that Ca(2+)-mediated negative feedback is responsible for the Weber-Fechner relationship between stimulus and response.
Ames
A
A
Neurosurgical Service, Massachusetts General Hospital, Boston 02114.
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000221:Adaptation, Ocular; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D003624:Darkness; D004056:Differential Threshold / Q000502:physiology; D005246:Feedback / Q000502:physiology; D006162:Guanylate Cyclase / Q000096:biosynthesis; D008027:Light; D008433:Mathematics; D008954:Models, Biological; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011817:Rabbits; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism*
D000242:Cyclic AMP; D010727:Phosphoric Diester Hydrolases; D006162:Guanylate Cyclase; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine