Non-independent quantum bumps in Limulus ventral nerve photoreceptors--a new insight in the light transduction mechanism.
Single photon-induced transient currents, called quantum bumps were stimulated by short flashes in dark-adapted ventral nerve photoreceptors of Limulus. Flash intensities were set to activate 3 or more bumps. In most cases, current bumps were activated with a constant rate. The frequency of bump occurrence was between 9 and 17 Hz. Results show that consecutive bumps are not independent and that some of them are not activated by a photon. The periodic bump activation indicates a molecular mechanism which quantifies the transmitter release not only by a light quantum, but also by a late phase of the transduction cascade. A model is proposed, in which Ca2+ ions released from intracellular stores transiently block the further Ca2+ release by inositol trisphosphate in an all-or-none manner.
Nagy
K
K
Institut für Biologie II, RWTH Aachen, FRG.
D000818:Animals; D002118:Calcium / Q000502:physiology; D005246:Feedback / Q000502:physiology; D006737:Horseshoe Crabs / Q000502:physiology*; D008027:Light; D010786:Photoreceptor Cells / Q000502:physiology*; D011827:Radiation; D015398:Signal Transduction / Q000502:physiology*
D002118:Calcium