HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Shiells, R. A. Articles by Falk, G. Search for Related Content PubMed PubMed Citation Articles by Shiells, R. A. Articles by Falk, G.

Activation of Ca²⁺-calmodulin kinase II induces desensitization by background light in dogfish retinal 'on' bipolar cells

R. A. Shiells and G. Falk

1. Retinal 'on' bipolar cells possess a metabotropic glutamate receptor (mGluR6) linked to the control of a G-protein and cGMP-activated channels which functions to generate high synaptic amplification of rod signals under dark-adapted conditions.

2. Desensitization of 'on' bipolar cells is initiated by a rise in Ca²⁺ during background light too weak to adapt rod photoreceptors. Desensitization could also be elicited by raising intracellular Ca²⁺ above 1 µM.

3. In order to investigate the mechanism of desensitization, whole-cell current responses to brief flashes and to steps of light were obtained from voltage-clamped 'on' bipolar cells in dark-adapted dogfish retinal slices. The inclusion of Ca²⁺-calmodulin kinase II (CaMKII) inhibitor peptides in the patch pipette solutions not only blocked desensitization of 'on' bipolar cells by dim background light and by 50 µM Ca²⁺, but also increased their flash sensitivity.

4. The substrate of phosphorylation by CaMKII is the 'on' bipolar cell cGMP-activated channels. Desensitization probably results from a reduction in their sensitivity to cGMP and a voltage-dependent decrease in their conductance.

5. A role for protein kinase C (PKC) in this process was excluded since activating PKC independently of Ca²⁺ with the phorbol ester PMA failed to induce desensitization of 'on' bipolar cells.

This article has been cited by other articles:

				S. Schein and K. M. Ahmad Efficiency of Synaptic Transmission of Single-Photon Events from Rod Photoreceptor to Rod Bipolar Dendrite Biophys. J., November 1, 2006; 91(9): 3257 - 3267. [Abstract] [Full Text] [PDF]

				S. Nawy Desensitization of the mGluR6 transduction current in tiger salamander On bipolar cells J. Physiol., July 1, 2004; 558(1): 137 - 146. [Abstract] [Full Text] [PDF]

				K. Djupsund, T. Furukawa, S. Yasui, and M. Yamada Asymmetric Temporal Properties in the Receptive Field of Retinal Transient Amacrine Cells J. Gen. Physiol., September 29, 2003; 122(4): 445 - 458. [Abstract] [Full Text] [PDF]

				A. Poli, A. Beraudi, L. Villani, M. Storto, G. Battaglia, V. Di Giorgi Gerevini, I. Cappuccio, A. Caricasole, M. D'Onofrio, and F. Nicoletti Group II Metabotropic Glutamate Receptors Regulate the Vulnerability to Hypoxic Brain Damage J. Neurosci., July 9, 2003; 23(14): 6023 - 6029. [Abstract] [Full Text] [PDF]

				J. Snellman and S. Nawy Regulation of the Retinal Bipolar Cell mGluR6 Pathway by Calcineurin J Neurophysiol, September 1, 2002; 88(3): 1088 - 1096. [Abstract] [Full Text] [PDF]