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1999 (1)
1975 (1)
1Author    SimonB. LaughlinRequires cookie*
 Title      
 Abstract    Intracellular recordings show that the receptors and second-order interneurons of the dragonfly compound eye change their sensitivity in response to maintained illumina­ tion. Comparison of receptor with interneuron shows that neural mechanisms act to ensure that the modulation of interneuron membrane potential that is set up by contrast changes is independent of background intensity. 
  Reference    (Z. Naturforsch. 30c, 306—308 [1975]; received January 3 1975) 
  Published    1975 
  Keywords    Dragonfly, Receptor, Interneuron, Light-adaptation 
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 DEBUG INFO      
 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0306_n.pdf 
 Identifier    ZNC-1975-30c-0306_n 
 Volume    30 
2Author    Marlies Dorlöchter, Weijia Yuan, Hennig StieveRequires cookie*
 Title    Effects of Calcium and Cyclopiazonic Acid on the Photoresponse in the Limulus Ventral Photoreceptor  
 Abstract    1. Single-photon responses (bumps) and small macroscopic photocurrents were studied in ventral photoreceptors of the horseshoe crab Limulus. Lowering the calcium concentration in the bath from 10 mM to 250 fiM led to increased bump size. Adaptation of the cells by a moderately bright conditioning flash was not impaired. 2. Pressure-injection of 1.2 mM EG TA into the dark-adapted cells resulted in reduced bump size. EG TA weakened the effect of the conditioning light flash although it did not completely abolish light adaptation. 3. The microsomal calcium-ATPase inhibitor cyclopiazonic acid strongly desensitized the cells, and bumps were suppressed below detection. When the bathing saline contained 10 m M calcium, macroscopic photoresponses after extracellular application of the agent had ampli­ tudes smaller than under control conditions but normal response kinetics: The response to a light step still consisted of a fast transient photocurrent and a much smaller plateau. How­ ever, when applied in calcium-free bathing saline, cyclopiazonic acid additionally influenced the waveform of the photoresponse. The clear distinction between transient and plateau was no longer possible, and the photocurrent appeared "square". 4. Our results support the idea that a transient elevation of the cytosolic calcium concentra­ tion is obligatory for light adaptation in the ventral photoreceptor. It is also obligatory for the generation of the so-called C2 component of the photocurrent which is represented by "standard" bumps and the fast transient phase of a prolonged response. However, a rise in cytosolic calcium appears not necessary for the initiation of a slow electrical photoresponse. 
  Reference    Z. Naturforsch. 54c, 446 (1999); received January 28/March 10 1999 
  Published    1999 
  Keywords    Phototransduction, Current Components, Light Adaptation, Bumps, CPA 
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 DEBUG INFO      
 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-0446.pdf 
 Identifier    ZNC-1999-54c-0446 
 Volume    54